diff --git a/browser/base/content/test/about/browser_aboutNewTab_bookmarksToolbarEmpty.js b/browser/base/content/test/about/browser_aboutNewTab_bookmarksToolbarEmpty.js
index deb3260326797..cb8bab2614082 100644
--- a/browser/base/content/test/about/browser_aboutNewTab_bookmarksToolbarEmpty.js
+++ b/browser/base/content/test/about/browser_aboutNewTab_bookmarksToolbarEmpty.js
@@ -18,7 +18,7 @@ const bookmarksInfo = [
   },
 ];
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     // Ensure we can wait for about:newtab to load.
     set: [["browser.newtab.preload", false]],
diff --git a/browser/base/content/test/alerts/browser_notification_do_not_disturb.js b/browser/base/content/test/alerts/browser_notification_do_not_disturb.js
index cfae32e216ca2..0cee5585621f7 100644
--- a/browser/base/content/test/alerts/browser_notification_do_not_disturb.js
+++ b/browser/base/content/test/alerts/browser_notification_do_not_disturb.js
@@ -20,7 +20,7 @@ const PAGE =
 // to show up before we decide that it's not coming.
 const NOTIFICATION_TIMEOUT_SECS = 2000;
 
-add_task(async function setup() {
+add_setup(async function() {
   await addNotificationPermission(PAGE);
 });
 
diff --git a/browser/base/content/test/captivePortal/browser_captivePortalTabReference.js b/browser/base/content/test/captivePortal/browser_captivePortalTabReference.js
index 63978a720e8ae..73297535acb12 100644
--- a/browser/base/content/test/captivePortal/browser_captivePortalTabReference.js
+++ b/browser/base/content/test/captivePortal/browser_captivePortalTabReference.js
@@ -40,7 +40,7 @@ async function checkCaptivePortalTabReference(evt, currState) {
   gBrowser.removeTab(errorTab);
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["captivedetect.canonicalURL", CANONICAL_URL],
diff --git a/browser/base/content/test/captivePortal/browser_captivePortal_certErrorUI.js b/browser/base/content/test/captivePortal/browser_captivePortal_certErrorUI.js
index 215f32d529fde..35d5bd64386fe 100644
--- a/browser/base/content/test/captivePortal/browser_captivePortal_certErrorUI.js
+++ b/browser/base/content/test/captivePortal/browser_captivePortal_certErrorUI.js
@@ -3,7 +3,7 @@
 
 "use strict";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["captivedetect.canonicalURL", CANONICAL_URL],
diff --git a/browser/base/content/test/captivePortal/browser_captivePortal_https_only.js b/browser/base/content/test/captivePortal/browser_captivePortal_https_only.js
index 5b58c3bcc730f..3e9e69201ced6 100644
--- a/browser/base/content/test/captivePortal/browser_captivePortal_https_only.js
+++ b/browser/base/content/test/captivePortal/browser_captivePortal_https_only.js
@@ -12,7 +12,7 @@ const testPath = getRootDirectory(gTestPath).replace(
 const CANONICAL_URI = Services.io.newURI(testPath);
 const PERMISSION_NAME = "https-only-load-insecure";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     // That changes the canoncicalURL from "http://{server}/captive-detect/success.txt"
     // to http://example.com
diff --git a/browser/base/content/test/captivePortal/browser_closeCapPortalTabCanonicalURL.js b/browser/base/content/test/captivePortal/browser_closeCapPortalTabCanonicalURL.js
index 22e38ca0b9c4e..bc30c95419807 100644
--- a/browser/base/content/test/captivePortal/browser_closeCapPortalTabCanonicalURL.js
+++ b/browser/base/content/test/captivePortal/browser_closeCapPortalTabCanonicalURL.js
@@ -35,7 +35,7 @@ function unlockHandler(request, response) {
   response.setHeader("Location", CANONICAL_SUCCESS_URL);
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // Set up a mock server for handling captive portal redirect.
   server = new HttpServer();
   server.registerPathHandler("/success", redirectHandler);
diff --git a/browser/base/content/test/contextMenu/browser_contextmenu_loadblobinnewtab.js b/browser/base/content/test/contextMenu/browser_contextmenu_loadblobinnewtab.js
index d8e7be99bf254..0154faf70a0dc 100644
--- a/browser/base/content/test/contextMenu/browser_contextmenu_loadblobinnewtab.js
+++ b/browser/base/content/test/contextMenu/browser_contextmenu_loadblobinnewtab.js
@@ -135,7 +135,7 @@ async function openInNewTabAndReturnContent(selector) {
   return blobDataFromContent;
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["privacy.partition.bloburl_per_agent_cluster", false]],
   });
diff --git a/browser/base/content/test/contextMenu/browser_contextmenu_touch.js b/browser/base/content/test/contextMenu/browser_contextmenu_touch.js
index 81e6462a380d5..f30e861d34120 100644
--- a/browser/base/content/test/contextMenu/browser_contextmenu_touch.js
+++ b/browser/base/content/test/contextMenu/browser_contextmenu_touch.js
@@ -35,7 +35,7 @@ async function openAndCheckContextMenu(contextMenu, target) {
 }
 
 // Ensure that we can run touch events properly for windows [10]
-add_task(async function setup() {
+add_setup(async function() {
   let isWindows = AppConstants.isPlatformAndVersionAtLeast("win", "10.0");
   await SpecialPowers.pushPrefEnv({
     set: [["apz.test.fails_with_native_injection", isWindows]],
diff --git a/browser/base/content/test/favicons/browser_preferred_icons.js b/browser/base/content/test/favicons/browser_preferred_icons.js
index 8b9893f264e25..ced7c27fec4ca 100644
--- a/browser/base/content/test/favicons/browser_preferred_icons.js
+++ b/browser/base/content/test/favicons/browser_preferred_icons.js
@@ -28,7 +28,7 @@ function createLinks(linkInfos) {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   const URL = ROOT + "discovery.html";
   let iconPromise = waitIcon("http://mochi.test:8888/favicon.ico");
   let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, URL);
diff --git a/browser/base/content/test/forms/browser_selectpopup.js b/browser/base/content/test/forms/browser_selectpopup.js
index 88573f38d2e3d..d7c0972792a5c 100644
--- a/browser/base/content/test/forms/browser_selectpopup.js
+++ b/browser/base/content/test/forms/browser_selectpopup.js
@@ -321,7 +321,7 @@ async function doSelectTests(contentType, content) {
   BrowserTestUtils.removeTab(tab);
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["dom.forms.select.customstyling", true]],
   });
diff --git a/browser/base/content/test/forms/browser_selectpopup_colors.js b/browser/base/content/test/forms/browser_selectpopup_colors.js
index d5b56f8bbe21b..9335916506901 100644
--- a/browser/base/content/test/forms/browser_selectpopup_colors.js
+++ b/browser/base/content/test/forms/browser_selectpopup_colors.js
@@ -459,7 +459,7 @@ async function testSelectColors(selectID, itemCount, options) {
 // System colors may be different in content pages and chrome pages.
 let kDefaultSelectStyles = {};
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["dom.forms.select.customstyling", true]],
   });
diff --git a/browser/base/content/test/forms/browser_selectpopup_searchfocus.js b/browser/base/content/test/forms/browser_selectpopup_searchfocus.js
index 72ce956cb0e15..bb7035406db96 100644
--- a/browser/base/content/test/forms/browser_selectpopup_searchfocus.js
+++ b/browser/base/content/test/forms/browser_selectpopup_searchfocus.js
@@ -6,7 +6,7 @@ SELECT +=
   '  <option selected="true">{"end": "true"}</option>' +
   "</select></body></html>";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["dom.forms.selectSearch", true]],
   });
diff --git a/browser/base/content/test/fullscreen/browser_fullscreen_window_focus.js b/browser/base/content/test/fullscreen/browser_fullscreen_window_focus.js
index d92de931d1aab..ac53cac54c582 100644
--- a/browser/base/content/test/fullscreen/browser_fullscreen_window_focus.js
+++ b/browser/base/content/test/fullscreen/browser_fullscreen_window_focus.js
@@ -76,7 +76,7 @@ async function testWindowElementFocus(isPopup) {
   BrowserTestUtils.removeTab(tab);
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["dom.disable_open_during_load", false], // Allow window.focus calls without user interaction
diff --git a/browser/base/content/test/fullscreen/browser_fullscreen_window_open.js b/browser/base/content/test/fullscreen/browser_fullscreen_window_open.js
index 460b6a0bf0bc0..1a853f0437b62 100644
--- a/browser/base/content/test/fullscreen/browser_fullscreen_window_open.js
+++ b/browser/base/content/test/fullscreen/browser_fullscreen_window_open.js
@@ -28,7 +28,7 @@ async function testWindowOpen(iframeID) {
   BrowserTestUtils.removeTab(tab);
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["dom.disable_open_during_load", false], // Allow window.open calls without user interaction
diff --git a/browser/base/content/test/general/browser_datachoices_notification.js b/browser/base/content/test/general/browser_datachoices_notification.js
index 38c1cc01ea7f9..78d864d739120 100644
--- a/browser/base/content/test/general/browser_datachoices_notification.js
+++ b/browser/base/content/test/general/browser_datachoices_notification.js
@@ -113,7 +113,7 @@ var checkInfobarButton = async function(aNotification) {
   await promiseNextTick();
 };
 
-add_task(async function setup() {
+add_setup(async function() {
   const isFirstRun = Preferences.get(PREF_FIRST_RUN, true);
   const bypassNotification = Preferences.get(PREF_BYPASS_NOTIFICATION, true);
   const currentPolicyVersion = Preferences.get(PREF_CURRENT_POLICY_VERSION, 1);
diff --git a/browser/base/content/test/general/browser_storagePressure_notification.js b/browser/base/content/test/general/browser_storagePressure_notification.js
index 7fe30af499e8d..2a720b3a3010a 100644
--- a/browser/base/content/test/general/browser_storagePressure_notification.js
+++ b/browser/base/content/test/general/browser_storagePressure_notification.js
@@ -27,7 +27,7 @@ function openAboutPrefPromise(win) {
   ];
   return Promise.all(promises);
 }
-add_task(async function setup() {
+add_setup(async function() {
   let win = await BrowserTestUtils.openNewBrowserWindow();
   // Open a new tab to keep the window open.
   await BrowserTestUtils.openNewForegroundTab(
diff --git a/browser/base/content/test/general/browser_unknownContentType_title.js b/browser/base/content/test/general/browser_unknownContentType_title.js
index 8ac32cdcb48dc..33d4c0d1016dd 100644
--- a/browser/base/content/test/general/browser_unknownContentType_title.js
+++ b/browser/base/content/test/general/browser_unknownContentType_title.js
@@ -16,7 +16,7 @@ function waitForNewWindow() {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   let tmpDir = PathUtils.join(
     PathUtils.tempDir,
     "testsavedir" + Math.floor(Math.random() * 2 ** 32)
diff --git a/browser/base/content/test/keyboard/browser_toolbarKeyNav.js b/browser/base/content/test/keyboard/browser_toolbarKeyNav.js
index cde12b057070c..07630db64c643 100644
--- a/browser/base/content/test/keyboard/browser_toolbarKeyNav.js
+++ b/browser/base/content/test/keyboard/browser_toolbarKeyNav.js
@@ -94,7 +94,7 @@ function withNewBlankTab(taskFn) {
 
 const BOOKMARKS_COUNT = 100;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.toolbars.keyboard_navigation", true],
diff --git a/browser/base/content/test/permissions/browser_autoplay_blocked.js b/browser/base/content/test/permissions/browser_autoplay_blocked.js
index a41f84766d80a..4fc8b40d626ad 100644
--- a/browser/base/content/test/permissions/browser_autoplay_blocked.js
+++ b/browser/base/content/test/permissions/browser_autoplay_blocked.js
@@ -73,7 +73,7 @@ function testPermListHasEntries(expectEntries) {
   ok(!listEntryCount, "List of permissions is empty");
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   registerCleanupFunction(() => {
     Services.perms.removeAll();
     Services.prefs.clearUserPref(AUTOPLAY_PREF);
diff --git a/browser/base/content/test/permissions/browser_permission_delegate_geo.js b/browser/base/content/test/permissions/browser_permission_delegate_geo.js
index 635d83ed15f83..316758d3ec545 100644
--- a/browser/base/content/test/permissions/browser_permission_delegate_geo.js
+++ b/browser/base/content/test/permissions/browser_permission_delegate_geo.js
@@ -112,7 +112,7 @@ async function checkGeolocation(browser, frameId, expect) {
   }
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await new Promise(r => {
     SpecialPowers.pushPrefEnv(
       {
diff --git a/browser/base/content/test/popupNotifications/browser_displayURI.js b/browser/base/content/test/popupNotifications/browser_displayURI.js
index 1d5b8ac44530a..43484913a0317 100644
--- a/browser/base/content/test/popupNotifications/browser_displayURI.js
+++ b/browser/base/content/test/popupNotifications/browser_displayURI.js
@@ -84,7 +84,7 @@ async function check(contentTask, options = {}) {
   }
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["media.navigator.permission.fake", true],
diff --git a/browser/base/content/test/popups/browser_popup_blocker.js b/browser/base/content/test/popups/browser_popup_blocker.js
index 5c01791954f04..70eb14a71f71f 100644
--- a/browser/base/content/test/popups/browser_popup_blocker.js
+++ b/browser/base/content/test/popups/browser_popup_blocker.js
@@ -15,7 +15,7 @@ function clearAllPermissionsByPrefix(aPrefix) {
   }
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // Enable the popup blocker.
   await SpecialPowers.pushPrefEnv({
     set: [["dom.disable_open_during_load", true]],
diff --git a/browser/base/content/test/protectionsUI/browser_protectionsUI.js b/browser/base/content/test/protectionsUI/browser_protectionsUI.js
index 0805374e84001..8dd901ea69096 100644
--- a/browser/base/content/test/protectionsUI/browser_protectionsUI.js
+++ b/browser/base/content/test/protectionsUI/browser_protectionsUI.js
@@ -18,7 +18,7 @@ const { CustomizableUITestUtils } = ChromeUtils.import(
   "resource://testing-common/CustomizableUITestUtils.jsm"
 );
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       // Set the auto hide timing to 100ms for blocking the test less.
diff --git a/browser/base/content/test/protectionsUI/browser_protectionsUI_cookies_subview.js b/browser/base/content/test/protectionsUI/browser_protectionsUI_cookies_subview.js
index 86bfb573cb05a..1fc28a37709b6 100644
--- a/browser/base/content/test/protectionsUI/browser_protectionsUI_cookies_subview.js
+++ b/browser/base/content/test/protectionsUI/browser_protectionsUI_cookies_subview.js
@@ -12,7 +12,7 @@ const CONTAINER_PAGE =
 
 const TPC_PREF = "network.cookie.cookieBehavior";
 
-add_task(async function setup() {
+add_setup(async function() {
   await UrlClassifierTestUtils.addTestTrackers();
 
   registerCleanupFunction(() => {
diff --git a/browser/base/content/test/protectionsUI/browser_protectionsUI_cryptominers.js b/browser/base/content/test/protectionsUI/browser_protectionsUI_cryptominers.js
index 8be2103071aec..d4a6d35363e08 100644
--- a/browser/base/content/test/protectionsUI/browser_protectionsUI_cryptominers.js
+++ b/browser/base/content/test/protectionsUI/browser_protectionsUI_cryptominers.js
@@ -8,7 +8,7 @@ const TRACKING_PAGE =
 const CM_PROTECTION_PREF = "privacy.trackingprotection.cryptomining.enabled";
 let cmHistogram;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       [
diff --git a/browser/base/content/test/protectionsUI/browser_protectionsUI_fingerprinters.js b/browser/base/content/test/protectionsUI/browser_protectionsUI_fingerprinters.js
index 441b465853dad..fcbeac2d16d45 100644
--- a/browser/base/content/test/protectionsUI/browser_protectionsUI_fingerprinters.js
+++ b/browser/base/content/test/protectionsUI/browser_protectionsUI_fingerprinters.js
@@ -8,7 +8,7 @@ const TRACKING_PAGE =
 const FP_PROTECTION_PREF = "privacy.trackingprotection.fingerprinting.enabled";
 let fpHistogram;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       [
diff --git a/browser/base/content/test/protectionsUI/browser_protectionsUI_milestones.js b/browser/base/content/test/protectionsUI/browser_protectionsUI_milestones.js
index 0748e9752d4a7..c61fd7a401bef 100644
--- a/browser/base/content/test/protectionsUI/browser_protectionsUI_milestones.js
+++ b/browser/base/content/test/protectionsUI/browser_protectionsUI_milestones.js
@@ -1,7 +1,7 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       // Hide protections cards so as not to trigger more async messaging
diff --git a/browser/base/content/test/protectionsUI/browser_protectionsUI_open_preferences.js b/browser/base/content/test/protectionsUI/browser_protectionsUI_open_preferences.js
index 0cad097569092..1b52fe55bb173 100644
--- a/browser/base/content/test/protectionsUI/browser_protectionsUI_open_preferences.js
+++ b/browser/base/content/test/protectionsUI/browser_protectionsUI_open_preferences.js
@@ -40,7 +40,7 @@ async function waitAndAssertPreferencesShown(_spotlight) {
   BrowserTestUtils.removeTab(gBrowser.selectedTab);
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await UrlClassifierTestUtils.addTestTrackers();
   let oldCanRecord = Services.telemetry.canRecordExtended;
   Services.telemetry.canRecordExtended = true;
diff --git a/browser/base/content/test/protectionsUI/browser_protectionsUI_report_breakage.js b/browser/base/content/test/protectionsUI/browser_protectionsUI_report_breakage.js
index abc503658b2da..1e1ed71189c74 100644
--- a/browser/base/content/test/protectionsUI/browser_protectionsUI_report_breakage.js
+++ b/browser/base/content/test/protectionsUI/browser_protectionsUI_report_breakage.js
@@ -23,7 +23,7 @@ let { Preferences } = ChromeUtils.import(
   "resource://gre/modules/Preferences.jsm"
 );
 
-add_task(async function setup() {
+add_setup(async function() {
   await UrlClassifierTestUtils.addTestTrackers();
 
   registerCleanupFunction(() => {
diff --git a/browser/base/content/test/protectionsUI/browser_protectionsUI_shield_visibility.js b/browser/base/content/test/protectionsUI/browser_protectionsUI_shield_visibility.js
index be3cc46118c61..4eb9b3247a791 100644
--- a/browser/base/content/test/protectionsUI/browser_protectionsUI_shield_visibility.js
+++ b/browser/base/content/test/protectionsUI/browser_protectionsUI_shield_visibility.js
@@ -74,7 +74,7 @@ const TEST_CASES = [
   },
 ];
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       // By default, proxies don't apply to 127.0.0.1. We need them to for this test, though:
diff --git a/browser/base/content/test/protectionsUI/browser_protectionsUI_socialtracking.js b/browser/base/content/test/protectionsUI/browser_protectionsUI_socialtracking.js
index 93a4b0dfc0e0a..ffea33f685d65 100644
--- a/browser/base/content/test/protectionsUI/browser_protectionsUI_socialtracking.js
+++ b/browser/base/content/test/protectionsUI/browser_protectionsUI_socialtracking.js
@@ -9,7 +9,7 @@ const TRACKING_PAGE =
 const ST_PROTECTION_PREF = "privacy.trackingprotection.socialtracking.enabled";
 const ST_BLOCK_COOKIES_PREF = "privacy.socialtracking.block_cookies.enabled";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       [ST_BLOCK_COOKIES_PREF, true],
diff --git a/browser/base/content/test/protectionsUI/browser_protectionsUI_subview_shim.js b/browser/base/content/test/protectionsUI/browser_protectionsUI_subview_shim.js
index 736b008253227..b3ae1b827efc4 100644
--- a/browser/base/content/test/protectionsUI/browser_protectionsUI_subview_shim.js
+++ b/browser/base/content/test/protectionsUI/browser_protectionsUI_subview_shim.js
@@ -14,7 +14,7 @@
 const TRACKING_PAGE =
   "http://example.net/browser/browser/base/content/test/protectionsUI/trackingPage.html";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["privacy.trackingprotection.enabled", true],
diff --git a/browser/base/content/test/protectionsUI/browser_protectionsUI_telemetry.js b/browser/base/content/test/protectionsUI/browser_protectionsUI_telemetry.js
index 70cc24b7fd16e..ffc8dedc1a7aa 100644
--- a/browser/base/content/test/protectionsUI/browser_protectionsUI_telemetry.js
+++ b/browser/base/content/test/protectionsUI/browser_protectionsUI_telemetry.js
@@ -29,7 +29,7 @@ function getShieldCounts() {
   return getShieldHistogram().snapshot().values;
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await UrlClassifierTestUtils.addTestTrackers();
   Services.prefs.setBoolPref(DTSCBN_PREF, true);
 
diff --git a/browser/base/content/test/protectionsUI/browser_protectionsUI_trackers_subview.js b/browser/base/content/test/protectionsUI/browser_protectionsUI_trackers_subview.js
index 3dea57cb75fd3..b500d066f1e92 100644
--- a/browser/base/content/test/protectionsUI/browser_protectionsUI_trackers_subview.js
+++ b/browser/base/content/test/protectionsUI/browser_protectionsUI_trackers_subview.js
@@ -13,7 +13,7 @@ const TRACKING_PAGE =
 
 const TP_PREF = "privacy.trackingprotection.enabled";
 
-add_task(async function setup() {
+add_setup(async function() {
   await UrlClassifierTestUtils.addTestTrackers();
 
   registerCleanupFunction(() => {
diff --git a/browser/base/content/test/sidebar/browser_sidebar_adopt.js b/browser/base/content/test/sidebar/browser_sidebar_adopt.js
index 58c155bed3c46..6d206e1b23aa4 100644
--- a/browser/base/content/test/sidebar/browser_sidebar_adopt.js
+++ b/browser/base/content/test/sidebar/browser_sidebar_adopt.js
@@ -12,7 +12,7 @@ function failIfSidebarFocusedFires() {
   ok(false, "This event shouldn't have fired");
 }
 
-add_task(function setup() {
+add_setup(function() {
   CustomizableUI.addWidgetToArea("sidebar-button", "nav-bar");
   registerCleanupFunction(() =>
     CustomizableUI.removeWidgetFromArea("sidebar-button")
diff --git a/browser/base/content/test/siteIdentity/browser_bug902156.js b/browser/base/content/test/siteIdentity/browser_bug902156.js
index 40b11851a306d..6eb6799dad5db 100644
--- a/browser/base/content/test/siteIdentity/browser_bug902156.js
+++ b/browser/base/content/test/siteIdentity/browser_bug902156.js
@@ -34,7 +34,7 @@ const HTTPS_TEST_ROOT_2 = getRootDirectory(gTestPath).replace(
   "https://test2.example.com"
 );
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({ set: [[PREF_ACTIVE, true]] });
 });
 
diff --git a/browser/base/content/test/sync/browser_contextmenu_sendpage.js b/browser/base/content/test/sync/browser_contextmenu_sendpage.js
index 882b2a93eab94..ced21e77116f1 100644
--- a/browser/base/content/test/sync/browser_contextmenu_sendpage.js
+++ b/browser/base/content/test/sync/browser_contextmenu_sendpage.js
@@ -27,7 +27,7 @@ const fxaDevices = [
   { id: 4, name: "Homer" }, // Incompatible target.
 ];
 
-add_task(async function setup() {
+add_setup(async function() {
   await promiseSyncReady();
   await Services.search.init();
   // gSync.init() is called in a requestIdleCallback. Force its initialization.
diff --git a/browser/base/content/test/sync/browser_contextmenu_sendtab.js b/browser/base/content/test/sync/browser_contextmenu_sendtab.js
index cb7cb4c894336..fe890c1c42ce2 100644
--- a/browser/base/content/test/sync/browser_contextmenu_sendtab.js
+++ b/browser/base/content/test/sync/browser_contextmenu_sendtab.js
@@ -50,7 +50,7 @@ function updateTabContextMenu(tab = gBrowser.selectedTab) {
   menu.hidePopup();
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await promiseSyncReady();
   await Services.search.init();
   // gSync.init() is called in a requestIdleCallback. Force its initialization.
diff --git a/browser/base/content/test/sync/browser_sync.js b/browser/base/content/test/sync/browser_sync.js
index 081ce930e1829..1143a94df8362 100644
--- a/browser/base/content/test/sync/browser_sync.js
+++ b/browser/base/content/test/sync/browser_sync.js
@@ -9,7 +9,7 @@ const { CustomizableUITestUtils } = ChromeUtils.import(
 
 let gCUITestUtils = new CustomizableUITestUtils(window);
 
-add_task(async function setup() {
+add_setup(async function() {
   // gSync.init() is called in a requestIdleCallback. Force its initialization.
   gSync.init();
   // This preference gets set the very first time that the FxA menu gets opened,
diff --git a/browser/base/content/test/tabPrompts/browser_confirmFolderUpload.js b/browser/base/content/test/tabPrompts/browser_confirmFolderUpload.js
index e9231647f9ed5..bbff8fa125b37 100644
--- a/browser/base/content/test/tabPrompts/browser_confirmFolderUpload.js
+++ b/browser/base/content/test/tabPrompts/browser_confirmFolderUpload.js
@@ -36,7 +36,7 @@ function getTestDirectory() {
   return tmpDir.path;
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       // Allow using our MockFilePicker in the content process.
diff --git a/browser/base/content/test/tabPrompts/browser_contentOrigins.js b/browser/base/content/test/tabPrompts/browser_contentOrigins.js
index 074727081939d..a9ae314bcd5b6 100644
--- a/browser/base/content/test/tabPrompts/browser_contentOrigins.js
+++ b/browser/base/content/test/tabPrompts/browser_contentOrigins.js
@@ -125,7 +125,7 @@ async function checkDialog(
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["prompts.contentPromptSubDialog", true],
diff --git a/browser/base/content/test/tabcrashed/browser_noPermanentKey.js b/browser/base/content/test/tabcrashed/browser_noPermanentKey.js
index 239938f9904ae..1fdcfaca96014 100644
--- a/browser/base/content/test/tabcrashed/browser_noPermanentKey.js
+++ b/browser/base/content/test/tabcrashed/browser_noPermanentKey.js
@@ -3,7 +3,7 @@
 const PAGE =
   "data:text/html,<html><body>A%20regular,%20everyday,%20normal%20page.";
 
-add_task(async function setup() {
+add_setup(async function() {
   await setupLocalCrashReportServer();
 });
 
diff --git a/browser/base/content/test/tabcrashed/browser_shown.js b/browser/base/content/test/tabcrashed/browser_shown.js
index 16e6a54feecef..92281a35d89e0 100644
--- a/browser/base/content/test/tabcrashed/browser_shown.js
+++ b/browser/base/content/test/tabcrashed/browser_shown.js
@@ -7,7 +7,7 @@ const COMMENTS = "Here's my test comment!";
 // Avoid timeouts, as in bug 1325530
 requestLongerTimeout(2);
 
-add_task(async function setup() {
+add_setup(async function() {
   await setupLocalCrashReportServer();
 });
 
diff --git a/browser/base/content/test/tabcrashed/browser_withoutDump.js b/browser/base/content/test/tabcrashed/browser_withoutDump.js
index fa261da434cf5..894950b002fab 100644
--- a/browser/base/content/test/tabcrashed/browser_withoutDump.js
+++ b/browser/base/content/test/tabcrashed/browser_withoutDump.js
@@ -3,7 +3,7 @@
 const PAGE =
   "data:text/html,<html><body>A%20regular,%20everyday,%20normal%20page.";
 
-add_task(async function setup() {
+add_setup(async function() {
   prepareNoDump();
 });
 
diff --git a/browser/base/content/test/tabdialogs/browser_tabdialogbox_content_prompts.js b/browser/base/content/test/tabdialogs/browser_tabdialogbox_content_prompts.js
index f0d2b4f42931d..0c84f3a35ae15 100644
--- a/browser/base/content/test/tabdialogs/browser_tabdialogbox_content_prompts.js
+++ b/browser/base/content/test/tabdialogs/browser_tabdialogbox_content_prompts.js
@@ -41,7 +41,7 @@ var commonDialogsBundle = Services.strings.createBundle(
 );
 
 // Setup.
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [[CONTENT_PROMPT_PREF, true]],
   });
diff --git a/browser/base/content/test/tabs/browser_multiselect_tabs_using_keyboard.js b/browser/base/content/test/tabs/browser_multiselect_tabs_using_keyboard.js
index 942bf75b1ca0c..fb622a2e686c3 100644
--- a/browser/base/content/test/tabs/browser_multiselect_tabs_using_keyboard.js
+++ b/browser/base/content/test/tabs/browser_multiselect_tabs_using_keyboard.js
@@ -15,7 +15,7 @@ function synthesizeKeyAndWaitForTabToGetKeyboardFocus(tab, keyCode, options) {
   return focused;
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // The DevEdition has the DevTools button in the toolbar by default. Remove it
   // to prevent branch-specific rules what button should be focused.
   CustomizableUI.removeWidgetFromArea("developer-button");
diff --git a/browser/base/content/test/tabs/browser_navigate_through_urls_origin_attributes.js b/browser/base/content/test/tabs/browser_navigate_through_urls_origin_attributes.js
index 9ab31b3d16519..ddce6f52d0b9f 100644
--- a/browser/base/content/test/tabs/browser_navigate_through_urls_origin_attributes.js
+++ b/browser/base/content/test/tabs/browser_navigate_through_urls_origin_attributes.js
@@ -33,7 +33,7 @@ var gPrevRemoteTypeRegularTab;
 var gPrevRemoteTypeContainerTab;
 var gPrevRemoteTypePrivateTab;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["privacy.userContext.enabled", true],
diff --git a/browser/base/content/test/tabs/browser_new_tab_in_privilegedabout_process_pref.js b/browser/base/content/test/tabs/browser_new_tab_in_privilegedabout_process_pref.js
index c6486b4cef314..270f138859f24 100644
--- a/browser/base/content/test/tabs/browser_new_tab_in_privilegedabout_process_pref.js
+++ b/browser/base/content/test/tabs/browser_new_tab_in_privilegedabout_process_pref.js
@@ -17,7 +17,7 @@ const ABOUT_NEWTAB = "about:newtab";
 const ABOUT_WELCOME = "about:welcome";
 const TEST_HTTP = "http://example.org/";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.newtab.preload", false],
diff --git a/browser/base/content/test/tabs/browser_origin_attrs_in_remote_type.js b/browser/base/content/test/tabs/browser_origin_attrs_in_remote_type.js
index 5631350828865..60d49847a93ed 100644
--- a/browser/base/content/test/tabs/browser_origin_attrs_in_remote_type.js
+++ b/browser/base/content/test/tabs/browser_origin_attrs_in_remote_type.js
@@ -21,7 +21,7 @@ var TEST_CASES = [
 const NUM_PAGES_OPEN_FOR_EACH_TEST_CASE = 5;
 var remoteTypes;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["privacy.userContext.enabled", true],
diff --git a/browser/base/content/test/tabs/browser_origin_attrs_rel.js b/browser/base/content/test/tabs/browser_origin_attrs_rel.js
index 5725cd11944de..eef0633526d5c 100644
--- a/browser/base/content/test/tabs/browser_origin_attrs_rel.js
+++ b/browser/base/content/test/tabs/browser_origin_attrs_rel.js
@@ -49,7 +49,7 @@ function handleEventLocal(aEvent) {
   }
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["privacy.userContext.enabled", true],
diff --git a/browser/base/content/test/tabs/browser_positional_attributes.js b/browser/base/content/test/tabs/browser_positional_attributes.js
index 50bdf92748e0c..be9b377e61dea 100644
--- a/browser/base/content/test/tabs/browser_positional_attributes.js
+++ b/browser/base/content/test/tabs/browser_positional_attributes.js
@@ -26,7 +26,7 @@ function testAttrib(tabIndex, attrib, expected) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   is(gBrowser.tabs.length, 1, "one tab is open initially");
 
   addTab("http://mochi.test:8888/#0");
diff --git a/browser/base/content/test/tabs/browser_privilegedmozilla_process_pref.js b/browser/base/content/test/tabs/browser_privilegedmozilla_process_pref.js
index 58be07b7a056b..b1a63c9d60502 100644
--- a/browser/base/content/test/tabs/browser_privilegedmozilla_process_pref.js
+++ b/browser/base/content/test/tabs/browser_privilegedmozilla_process_pref.js
@@ -17,7 +17,7 @@ const TEST_HIGH2 = "https://test1.example.org/";
 const TEST_LOW1 = "http://example.org/";
 const TEST_LOW2 = "https://example.com/";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.tabs.remote.separatePrivilegedMozillaWebContentProcess", true],
diff --git a/browser/base/content/test/tabs/browser_progress_keyword_search_handling.js b/browser/base/content/test/tabs/browser_progress_keyword_search_handling.js
index 99af24ac8f1e1..19b630b8115a7 100644
--- a/browser/base/content/test/tabs/browser_progress_keyword_search_handling.js
+++ b/browser/base/content/test/tabs/browser_progress_keyword_search_handling.js
@@ -11,7 +11,7 @@ SearchTestUtils.init(this);
 
 const kButton = document.getElementById("reload-button");
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["browser.fixup.dns_first_for_single_words", true]],
   });
diff --git a/browser/base/content/test/tabs/browser_removeTabs_order.js b/browser/base/content/test/tabs/browser_removeTabs_order.js
index fe6dd885a6bd2..c0e9cc84ad4ac 100644
--- a/browser/base/content/test/tabs/browser_removeTabs_order.js
+++ b/browser/base/content/test/tabs/browser_removeTabs_order.js
@@ -5,7 +5,7 @@
 
 const { sinon } = ChromeUtils.import("resource://testing-common/Sinon.jsm");
 
-add_task(async function setup() {
+add_setup(async function() {
   let tab1 = await addTab();
   let tab2 = await addTab();
   let tab3 = await addTab();
diff --git a/browser/base/content/test/tabs/browser_removeTabs_skipPermitUnload.js b/browser/base/content/test/tabs/browser_removeTabs_skipPermitUnload.js
index a26375282b979..1db1b22195ca2 100644
--- a/browser/base/content/test/tabs/browser_removeTabs_skipPermitUnload.js
+++ b/browser/base/content/test/tabs/browser_removeTabs_skipPermitUnload.js
@@ -38,7 +38,7 @@ let win;
 let nonBeforeUnloadTab;
 let beforeUnloadTab;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["dom.require_user_interaction_for_beforeunload", false]],
   });
diff --git a/browser/base/content/test/tabs/browser_tabCloseProbes.js b/browser/base/content/test/tabs/browser_tabCloseProbes.js
index 3bc547ccb816d..c5b69567efedf 100644
--- a/browser/base/content/test/tabs/browser_tabCloseProbes.js
+++ b/browser/base/content/test/tabs/browser_tabCloseProbes.js
@@ -58,7 +58,7 @@ function waitForSnapshotCount(histogram, expectedCount) {
   }, `Collected value should become ${expectedCount}.`);
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // Force-enable tab animations
   gReduceMotionOverride = false;
 
diff --git a/browser/base/content/test/tabs/browser_tabSpinnerProbe.js b/browser/base/content/test/tabs/browser_tabSpinnerProbe.js
index 0a27b6f3ea02d..bd7501443aaeb 100644
--- a/browser/base/content/test/tabs/browser_tabSpinnerProbe.js
+++ b/browser/base/content/test/tabs/browser_tabSpinnerProbe.js
@@ -82,7 +82,7 @@ async function testProbe(aProbe) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["dom.ipc.processCount", 1],
diff --git a/browser/base/content/test/touch/browser_menu_touch.js b/browser/base/content/test/touch/browser_menu_touch.js
index bdb2bf53a02f2..3dc5c5193c927 100644
--- a/browser/base/content/test/touch/browser_menu_touch.js
+++ b/browser/base/content/test/touch/browser_menu_touch.js
@@ -112,7 +112,7 @@ async function openAndCheckCustomizationUIMenu(target) {
 }
 
 // Ensure that we can run touch events properly for windows [10]
-add_task(async function setup() {
+add_setup(async function() {
   let isWindows = AppConstants.isPlatformAndVersionAtLeast("win", "10.0");
   await SpecialPowers.pushPrefEnv({
     set: [["apz.test.fails_with_native_injection", isWindows]],
diff --git a/browser/base/content/test/webextensions/browser_extension_update_background.js b/browser/base/content/test/webextensions/browser_extension_update_background.js
index 89a2630bbd438..3647c0790151f 100644
--- a/browser/base/content/test/webextensions/browser_extension_update_background.js
+++ b/browser/base/content/test/webextensions/browser_extension_update_background.js
@@ -35,7 +35,7 @@ function getBadgeStatus() {
 }
 
 // Set some prefs that apply to all the tests in this file
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       // We don't have pre-pinned certificates for the local mochitest server
diff --git a/browser/base/content/test/webextensions/browser_extension_update_background_noprompt.js b/browser/base/content/test/webextensions/browser_extension_update_background_noprompt.js
index 388988a4f97f0..bdc1f09d51a75 100644
--- a/browser/base/content/test/webextensions/browser_extension_update_background_noprompt.js
+++ b/browser/base/content/test/webextensions/browser_extension_update_background_noprompt.js
@@ -20,7 +20,7 @@ function getBadgeStatus() {
 }
 
 // Set some prefs that apply to all the tests in this file
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       // We don't have pre-pinned certificates for the local mochitest server
diff --git a/browser/base/content/test/webextensions/browser_permissions_dismiss.js b/browser/base/content/test/webextensions/browser_permissions_dismiss.js
index 394ab8abe5028..9ab63c56f156b 100644
--- a/browser/base/content/test/webextensions/browser_permissions_dismiss.js
+++ b/browser/base/content/test/webextensions/browser_permissions_dismiss.js
@@ -3,7 +3,7 @@
 const INSTALL_PAGE = `${BASE}/file_install_extensions.html`;
 const INSTALL_XPI = `${BASE}/browser_webext_permissions.xpi`;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["extensions.webapi.testing", true],
diff --git a/browser/base/content/test/webextensions/browser_update_interactive_noprompt.js b/browser/base/content/test/webextensions/browser_update_interactive_noprompt.js
index 67054cf266e29..7de49d35663aa 100644
--- a/browser/base/content/test/webextensions/browser_update_interactive_noprompt.js
+++ b/browser/base/content/test/webextensions/browser_update_interactive_noprompt.js
@@ -1,5 +1,5 @@
 // Set some prefs that apply to all the tests in this file
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       // We don't have pre-pinned certificates for the local mochitest server
diff --git a/browser/base/content/test/webrtc/browser_global_mute_toggles.js b/browser/base/content/test/webrtc/browser_global_mute_toggles.js
index ce7c31904456a..37478f4688dc4 100644
--- a/browser/base/content/test/webrtc/browser_global_mute_toggles.js
+++ b/browser/base/content/test/webrtc/browser_global_mute_toggles.js
@@ -15,7 +15,7 @@ const MUTE_TOPICS = [
   "getUserMedia:unmuteAudio",
 ];
 
-add_task(async function setup() {
+add_setup(async function() {
   let prefs = [
     [PREF_PERMISSION_FAKE, true],
     [PREF_AUDIO_LOOPBACK, ""],
diff --git a/browser/base/content/test/webrtc/browser_notification_silencing.js b/browser/base/content/test/webrtc/browser_notification_silencing.js
index bba88b052c9c3..88591952858ea 100644
--- a/browser/base/content/test/webrtc/browser_notification_silencing.js
+++ b/browser/base/content/test/webrtc/browser_notification_silencing.js
@@ -129,7 +129,7 @@ async function testNotificationSilencing(aBrowser) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // Set prefs so that permissions prompts are shown and loopback devices
   // are not used. To test the chrome we want prompts to be shown, and
   // these tests are flakey when using loopback devices (though it would
diff --git a/browser/base/content/test/webrtc/browser_stop_sharing_button.js b/browser/base/content/test/webrtc/browser_stop_sharing_button.js
index 686ffc7065ab1..db9cc0d1fee08 100644
--- a/browser/base/content/test/webrtc/browser_stop_sharing_button.js
+++ b/browser/base/content/test/webrtc/browser_stop_sharing_button.js
@@ -9,7 +9,7 @@ const TEST_ROOT = getRootDirectory(gTestPath).replace(
 );
 const TEST_PAGE = TEST_ROOT + "get_user_media.html";
 
-add_task(async function setup() {
+add_setup(async function() {
   let prefs = [
     [PREF_PERMISSION_FAKE, true],
     [PREF_AUDIO_LOOPBACK, ""],
diff --git a/browser/base/content/test/webrtc/browser_stop_streams_on_indicator_close.js b/browser/base/content/test/webrtc/browser_stop_streams_on_indicator_close.js
index a34df440477db..b0863dab61ca1 100644
--- a/browser/base/content/test/webrtc/browser_stop_streams_on_indicator_close.js
+++ b/browser/base/content/test/webrtc/browser_stop_streams_on_indicator_close.js
@@ -9,7 +9,7 @@ const TEST_ROOT = getRootDirectory(gTestPath).replace(
 );
 const TEST_PAGE = TEST_ROOT + "get_user_media.html";
 
-add_task(async function setup() {
+add_setup(async function() {
   let prefs = [
     [PREF_PERMISSION_FAKE, true],
     [PREF_AUDIO_LOOPBACK, ""],
diff --git a/browser/base/content/test/webrtc/browser_tab_switch_warning.js b/browser/base/content/test/webrtc/browser_tab_switch_warning.js
index 30583722ef22e..2f6519bc136fd 100644
--- a/browser/base/content/test/webrtc/browser_tab_switch_warning.js
+++ b/browser/base/content/test/webrtc/browser_tab_switch_warning.js
@@ -188,7 +188,7 @@ async function ensureWarning(tab) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["privacy.webrtc.sharedTabWarning", true]],
   });
diff --git a/browser/components/aboutlogins/tests/browser/browser_aaa_eventTelemetry_run_first.js b/browser/components/aboutlogins/tests/browser/browser_aaa_eventTelemetry_run_first.js
index 7b5aec3550ab9..adc549d25fce2 100644
--- a/browser/components/aboutlogins/tests/browser/browser_aaa_eventTelemetry_run_first.js
+++ b/browser/components/aboutlogins/tests/browser/browser_aaa_eventTelemetry_run_first.js
@@ -30,7 +30,7 @@ let VULNERABLE_TEST_LOGIN2 = new nsLoginInfo(
   "password"
 );
 
-add_task(async function setup() {
+add_setup(async function() {
   TEST_LOGIN1 = await addLogin(TEST_LOGIN1);
   VULNERABLE_TEST_LOGIN2 = await addLogin(VULNERABLE_TEST_LOGIN2);
   TEST_LOGIN3 = await addLogin(TEST_LOGIN3);
diff --git a/browser/components/aboutlogins/tests/browser/browser_alertDismissedAfterChangingPassword.js b/browser/components/aboutlogins/tests/browser/browser_alertDismissedAfterChangingPassword.js
index 88a025bed3385..67f68adfa37e1 100644
--- a/browser/components/aboutlogins/tests/browser/browser_alertDismissedAfterChangingPassword.js
+++ b/browser/components/aboutlogins/tests/browser/browser_alertDismissedAfterChangingPassword.js
@@ -24,7 +24,7 @@ let VULNERABLE_TEST_LOGIN2 = new nsLoginInfo(
   "password"
 );
 
-add_task(async function setup() {
+add_setup(async function() {
   TEST_LOGIN1 = await addLogin(TEST_LOGIN1);
   VULNERABLE_TEST_LOGIN2 = await addLogin(VULNERABLE_TEST_LOGIN2);
   TEST_LOGIN3 = await addLogin(TEST_LOGIN3);
diff --git a/browser/components/aboutlogins/tests/browser/browser_breachAlertShowingForAddedLogin.js b/browser/components/aboutlogins/tests/browser/browser_breachAlertShowingForAddedLogin.js
index 394f9041f9422..78c819c6a076a 100644
--- a/browser/components/aboutlogins/tests/browser/browser_breachAlertShowingForAddedLogin.js
+++ b/browser/components/aboutlogins/tests/browser/browser_breachAlertShowingForAddedLogin.js
@@ -14,7 +14,7 @@ EXPECTED_BREACH = {
   schema: "1541615609018",
 };
 
-add_task(async function setup() {
+add_setup(async function() {
   await BrowserTestUtils.openNewForegroundTab({
     gBrowser,
     url: "about:logins",
diff --git a/browser/components/aboutlogins/tests/browser/browser_confirmDeleteDialog.js b/browser/components/aboutlogins/tests/browser/browser_confirmDeleteDialog.js
index ca37821608ff4..6a5a94f222595 100644
--- a/browser/components/aboutlogins/tests/browser/browser_confirmDeleteDialog.js
+++ b/browser/components/aboutlogins/tests/browser/browser_confirmDeleteDialog.js
@@ -1,7 +1,7 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
-add_task(async function setup() {
+add_setup(async function() {
   await BrowserTestUtils.openNewForegroundTab({
     gBrowser,
     url: "about:logins",
diff --git a/browser/components/aboutlogins/tests/browser/browser_contextmenuFillLogins.js b/browser/components/aboutlogins/tests/browser/browser_contextmenuFillLogins.js
index 2521432eb624c..0eb9c70459a18 100644
--- a/browser/components/aboutlogins/tests/browser/browser_contextmenuFillLogins.js
+++ b/browser/components/aboutlogins/tests/browser/browser_contextmenuFillLogins.js
@@ -1,7 +1,7 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
-add_task(async function setup() {
+add_setup(async function() {
   TEST_LOGIN1 = await addLogin(TEST_LOGIN1);
   await BrowserTestUtils.openNewForegroundTab({
     gBrowser,
diff --git a/browser/components/aboutlogins/tests/browser/browser_createLogin.js b/browser/components/aboutlogins/tests/browser/browser_createLogin.js
index a886792f6570b..109979e2c4c69 100644
--- a/browser/components/aboutlogins/tests/browser/browser_createLogin.js
+++ b/browser/components/aboutlogins/tests/browser/browser_createLogin.js
@@ -1,7 +1,7 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
-add_task(async function setup() {
+add_setup(async function() {
   let aboutLoginsTab = await BrowserTestUtils.openNewForegroundTab({
     gBrowser,
     url: "about:logins",
diff --git a/browser/components/aboutlogins/tests/browser/browser_deleteLogin.js b/browser/components/aboutlogins/tests/browser/browser_deleteLogin.js
index e8971a6a178d9..2e192844f25b7 100644
--- a/browser/components/aboutlogins/tests/browser/browser_deleteLogin.js
+++ b/browser/components/aboutlogins/tests/browser/browser_deleteLogin.js
@@ -1,7 +1,7 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
-add_task(async function setup() {
+add_setup(async function() {
   TEST_LOGIN1 = await addLogin(TEST_LOGIN1);
   TEST_LOGIN2 = await addLogin(TEST_LOGIN2);
   await BrowserTestUtils.openNewForegroundTab({
diff --git a/browser/components/aboutlogins/tests/browser/browser_fxAccounts.js b/browser/components/aboutlogins/tests/browser/browser_fxAccounts.js
index 200032d6d4090..c9306d0915f5c 100644
--- a/browser/components/aboutlogins/tests/browser/browser_fxAccounts.js
+++ b/browser/components/aboutlogins/tests/browser/browser_fxAccounts.js
@@ -12,7 +12,7 @@ function mockState(state) {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   let aboutLoginsTab = await BrowserTestUtils.openNewForegroundTab({
     gBrowser,
     url: "about:logins",
diff --git a/browser/components/aboutlogins/tests/browser/browser_loginItemErrors.js b/browser/components/aboutlogins/tests/browser/browser_loginItemErrors.js
index f6be325e4093b..4adf69203c707 100644
--- a/browser/components/aboutlogins/tests/browser/browser_loginItemErrors.js
+++ b/browser/components/aboutlogins/tests/browser/browser_loginItemErrors.js
@@ -1,7 +1,7 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
-add_task(async function setup() {
+add_setup(async function() {
   await BrowserTestUtils.openNewForegroundTab({
     gBrowser,
     url: "about:logins",
diff --git a/browser/components/aboutlogins/tests/browser/browser_loginListChanges.js b/browser/components/aboutlogins/tests/browser/browser_loginListChanges.js
index 1a51bb2e64a74..910e8d5be7e92 100644
--- a/browser/components/aboutlogins/tests/browser/browser_loginListChanges.js
+++ b/browser/components/aboutlogins/tests/browser/browser_loginListChanges.js
@@ -1,7 +1,7 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
-add_task(async function setup() {
+add_setup(async function() {
   await BrowserTestUtils.openNewForegroundTab({
     gBrowser,
     url: "about:logins",
diff --git a/browser/components/aboutlogins/tests/browser/browser_loginSortOrderRestored.js b/browser/components/aboutlogins/tests/browser/browser_loginSortOrderRestored.js
index fc77a149bddb6..937bfa210a770 100644
--- a/browser/components/aboutlogins/tests/browser/browser_loginSortOrderRestored.js
+++ b/browser/components/aboutlogins/tests/browser/browser_loginSortOrderRestored.js
@@ -16,7 +16,7 @@ EXPECTED_BREACH = {
 
 const SORT_PREF_NAME = "signon.management.page.sort";
 
-add_task(async function setup() {
+add_setup(async function() {
   TEST_LOGIN3.QueryInterface(Ci.nsILoginMetaInfo).timePasswordChanged = 1;
   TEST_LOGIN1 = await addLogin(TEST_LOGIN1);
   info(`TEST_LOGIN1 added with guid=${TEST_LOGIN1.guid}`);
diff --git a/browser/components/aboutlogins/tests/browser/browser_noLoginsView.js b/browser/components/aboutlogins/tests/browser/browser_noLoginsView.js
index e67852642887a..e2cfdbd883c1a 100644
--- a/browser/components/aboutlogins/tests/browser/browser_noLoginsView.js
+++ b/browser/components/aboutlogins/tests/browser/browser_noLoginsView.js
@@ -1,7 +1,7 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
-add_task(async function setup() {
+add_setup(async function() {
   await BrowserTestUtils.openNewForegroundTab({
     gBrowser,
     url: "about:logins",
diff --git a/browser/components/aboutlogins/tests/browser/browser_openExport.js b/browser/components/aboutlogins/tests/browser/browser_openExport.js
index 810b92e0c2b11..fe5f668c34637 100644
--- a/browser/components/aboutlogins/tests/browser/browser_openExport.js
+++ b/browser/components/aboutlogins/tests/browser/browser_openExport.js
@@ -17,7 +17,7 @@ let { TelemetryTestUtils } = ChromeUtils.import(
 
 let { MockFilePicker } = SpecialPowers;
 
-add_task(async function setup() {
+add_setup(async function() {
   await TestUtils.waitForCondition(() => {
     Services.telemetry.clearEvents();
     let events = Services.telemetry.snapshotEvents(
diff --git a/browser/components/aboutlogins/tests/browser/browser_openFiltered.js b/browser/components/aboutlogins/tests/browser/browser_openFiltered.js
index b8eba0c08208c..aaa4d75fafbcc 100644
--- a/browser/components/aboutlogins/tests/browser/browser_openFiltered.js
+++ b/browser/components/aboutlogins/tests/browser/browser_openFiltered.js
@@ -1,7 +1,7 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
-add_task(async function setup() {
+add_setup(async function() {
   let storageChangedPromised = TestUtils.topicObserved(
     "passwordmgr-storage-changed",
     (_, data) => data == "addLogin"
diff --git a/browser/components/aboutlogins/tests/browser/browser_openImport.js b/browser/components/aboutlogins/tests/browser/browser_openImport.js
index abe1ae917e090..aac7d47929c31 100644
--- a/browser/components/aboutlogins/tests/browser/browser_openImport.js
+++ b/browser/components/aboutlogins/tests/browser/browser_openImport.js
@@ -5,7 +5,7 @@ let { TelemetryTestUtils } = ChromeUtils.import(
   "resource://testing-common/TelemetryTestUtils.jsm"
 );
 
-add_task(async function setup() {
+add_setup(async function() {
   await TestUtils.waitForCondition(() => {
     Services.telemetry.clearEvents();
     let events = Services.telemetry.snapshotEvents(
diff --git a/browser/components/aboutlogins/tests/browser/browser_openImportCSV.js b/browser/components/aboutlogins/tests/browser/browser_openImportCSV.js
index 2984b854667fa..c52ea6c8df478 100644
--- a/browser/components/aboutlogins/tests/browser/browser_openImportCSV.js
+++ b/browser/components/aboutlogins/tests/browser/browser_openImportCSV.js
@@ -257,7 +257,7 @@ class CsvImportHelper {
 
 const random = Math.round(Math.random() * 100000001);
 
-add_task(async function setup() {
+add_setup(async function() {
   registerCleanupFunction(() => {
     Services.logins.removeAllUserFacingLogins();
   });
diff --git a/browser/components/aboutlogins/tests/browser/browser_openPreferences.js b/browser/components/aboutlogins/tests/browser/browser_openPreferences.js
index 876ee2a7a3cff..cc3e34484c4e5 100644
--- a/browser/components/aboutlogins/tests/browser/browser_openPreferences.js
+++ b/browser/components/aboutlogins/tests/browser/browser_openPreferences.js
@@ -5,7 +5,7 @@ let { TelemetryTestUtils } = ChromeUtils.import(
   "resource://testing-common/TelemetryTestUtils.jsm"
 );
 
-add_task(async function setup() {
+add_setup(async function() {
   await TestUtils.waitForCondition(() => {
     Services.telemetry.clearEvents();
     let events = Services.telemetry.snapshotEvents(
diff --git a/browser/components/aboutlogins/tests/browser/browser_openPreferencesExternal.js b/browser/components/aboutlogins/tests/browser/browser_openPreferencesExternal.js
index adac8f03a0314..591bb3b9112e0 100644
--- a/browser/components/aboutlogins/tests/browser/browser_openPreferencesExternal.js
+++ b/browser/components/aboutlogins/tests/browser/browser_openPreferencesExternal.js
@@ -1,7 +1,7 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
-add_task(async function setup() {
+add_setup(async function() {
   await BrowserTestUtils.openNewForegroundTab({
     gBrowser,
     url: "about:logins",
diff --git a/browser/components/aboutlogins/tests/browser/browser_openSite.js b/browser/components/aboutlogins/tests/browser/browser_openSite.js
index 92934f8adafc8..ad6b8436997e4 100644
--- a/browser/components/aboutlogins/tests/browser/browser_openSite.js
+++ b/browser/components/aboutlogins/tests/browser/browser_openSite.js
@@ -1,7 +1,7 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
-add_task(async function setup() {
+add_setup(async function() {
   TEST_LOGIN1 = await addLogin(TEST_LOGIN1);
   await BrowserTestUtils.openNewForegroundTab({
     gBrowser,
diff --git a/browser/components/aboutlogins/tests/browser/browser_primaryPassword.js b/browser/components/aboutlogins/tests/browser/browser_primaryPassword.js
index 6bd89b6ad9db4..1615c3026800c 100644
--- a/browser/components/aboutlogins/tests/browser/browser_primaryPassword.js
+++ b/browser/components/aboutlogins/tests/browser/browser_primaryPassword.js
@@ -17,7 +17,7 @@ function waitForLoginCountToReach(browser, loginCount) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await addLogin(TEST_LOGIN1);
   registerCleanupFunction(() => {
     Services.logins.removeAllUserFacingLogins();
diff --git a/browser/components/aboutlogins/tests/browser/browser_removeAllDialog.js b/browser/components/aboutlogins/tests/browser/browser_removeAllDialog.js
index a465a3f44ad7d..83eae83f1ef72 100644
--- a/browser/components/aboutlogins/tests/browser/browser_removeAllDialog.js
+++ b/browser/components/aboutlogins/tests/browser/browser_removeAllDialog.js
@@ -76,7 +76,7 @@ async function waitForRemoveAllLogins() {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [[OS_REAUTH_PREF, false]],
   });
diff --git a/browser/components/aboutlogins/tests/browser/browser_tabKeyNav.js b/browser/components/aboutlogins/tests/browser/browser_tabKeyNav.js
index e18ed44ed7f43..d9b59458a33b4 100644
--- a/browser/components/aboutlogins/tests/browser/browser_tabKeyNav.js
+++ b/browser/components/aboutlogins/tests/browser/browser_tabKeyNav.js
@@ -14,7 +14,7 @@ EXPECTED_BREACH = {
   schema: "1541615609018",
 };
 
-add_task(async function setup() {
+add_setup(async function() {
   TEST_LOGIN1 = await addLogin(TEST_LOGIN1);
   await BrowserTestUtils.openNewForegroundTab({
     gBrowser,
diff --git a/browser/components/aboutlogins/tests/browser/browser_updateLogin.js b/browser/components/aboutlogins/tests/browser/browser_updateLogin.js
index 2bef81db41163..eeaa6ec56d809 100644
--- a/browser/components/aboutlogins/tests/browser/browser_updateLogin.js
+++ b/browser/components/aboutlogins/tests/browser/browser_updateLogin.js
@@ -1,7 +1,7 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
-add_task(async function setup() {
+add_setup(async function() {
   TEST_LOGIN1 = await addLogin(TEST_LOGIN1);
   await BrowserTestUtils.openNewForegroundTab({
     gBrowser,
diff --git a/browser/components/aboutlogins/tests/browser/browser_vulnerableLoginAddedInSecondaryWindow.js b/browser/components/aboutlogins/tests/browser/browser_vulnerableLoginAddedInSecondaryWindow.js
index 4f3894b218ad7..3c0427dd3ca6c 100644
--- a/browser/components/aboutlogins/tests/browser/browser_vulnerableLoginAddedInSecondaryWindow.js
+++ b/browser/components/aboutlogins/tests/browser/browser_vulnerableLoginAddedInSecondaryWindow.js
@@ -16,7 +16,7 @@ EXPECTED_BREACH = {
 
 let tabInSecondWindow;
 
-add_task(async function setup() {
+add_setup(async function() {
   TEST_LOGIN1 = await addLogin(TEST_LOGIN1);
   TEST_LOGIN2 = await addLogin(TEST_LOGIN2);
   TEST_LOGIN3 = await addLogin(TEST_LOGIN3);
diff --git a/browser/components/attribution/test/browser/head.js b/browser/components/attribution/test/browser/head.js
index cd4124d272f81..973e63d2fb36b 100644
--- a/browser/components/attribution/test/browser/head.js
+++ b/browser/components/attribution/test/browser/head.js
@@ -13,7 +13,7 @@ const INDEX_DECODE_ERROR = 1;
 const INDEX_WRITE_ERROR = 2;
 const INDEX_QUARANTINE_ERROR = 3;
 
-add_task(function setup() {
+add_setup(function() {
   // AttributionCode._clearCache is only possible in a testing environment
   let env = Cc["@mozilla.org/process/environment;1"].getService(
     Ci.nsIEnvironment
diff --git a/browser/components/contextualidentity/test/browser/browser_blobUrl.js b/browser/components/contextualidentity/test/browser/browser_blobUrl.js
index 0fcb9bf6e43d1..4469f56fc3a6b 100644
--- a/browser/components/contextualidentity/test/browser/browser_blobUrl.js
+++ b/browser/components/contextualidentity/test/browser/browser_blobUrl.js
@@ -6,7 +6,7 @@ const BASE_URI =
   "http://mochi.test:8888/browser/browser/components/" +
   "contextualidentity/test/browser/empty_file.html";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["privacy.userContext.enabled", true]],
   });
diff --git a/browser/components/contextualidentity/test/browser/browser_broadcastchannel.js b/browser/components/contextualidentity/test/browser/browser_broadcastchannel.js
index 4bce3fbc7f96e..cc3354fbeb675 100644
--- a/browser/components/contextualidentity/test/browser/browser_broadcastchannel.js
+++ b/browser/components/contextualidentity/test/browser/browser_broadcastchannel.js
@@ -68,7 +68,7 @@ async function runTestForReceiver(receiver) {
   gBrowser.removeTab(sender2.tab);
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // make sure userContext is enabled.
   await SpecialPowers.pushPrefEnv({
     set: [["privacy.userContext.enabled", true]],
diff --git a/browser/components/contextualidentity/test/browser/browser_count_and_remove.js b/browser/components/contextualidentity/test/browser/browser_count_and_remove.js
index 7d9d2f6d087a6..214de40256187 100644
--- a/browser/components/contextualidentity/test/browser/browser_count_and_remove.js
+++ b/browser/components/contextualidentity/test/browser/browser_count_and_remove.js
@@ -10,7 +10,7 @@ function openTabInUserContext(userContextId) {
   gBrowser.selectedTab = tab;
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // make sure userContext is enabled.
   await SpecialPowers.pushPrefEnv({
     set: [["privacy.userContext.enabled", true]],
diff --git a/browser/components/contextualidentity/test/browser/browser_eme.js b/browser/components/contextualidentity/test/browser/browser_eme.js
index 4c6111e087838..62c2b22d385bb 100644
--- a/browser/components/contextualidentity/test/browser/browser_eme.js
+++ b/browser/components/contextualidentity/test/browser/browser_eme.js
@@ -90,7 +90,7 @@ function generateKeyInfo(aData) {
   return keyInfo;
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // Make sure userContext is enabled.
   await SpecialPowers.pushPrefEnv({
     set: [
diff --git a/browser/components/contextualidentity/test/browser/browser_favicon.js b/browser/components/contextualidentity/test/browser/browser_favicon.js
index 151f40861e39c..dd9f2f8e34378 100644
--- a/browser/components/contextualidentity/test/browser/browser_favicon.js
+++ b/browser/components/contextualidentity/test/browser/browser_favicon.js
@@ -78,7 +78,7 @@ function loadFaviconHandler(metadata, response) {
   response.bodyOutputStream.write(gFaviconData, gFaviconData.length);
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // Make sure userContext is enabled.
   await SpecialPowers.pushPrefEnv({
     set: [["privacy.userContext.enabled", true]],
diff --git a/browser/components/contextualidentity/test/browser/browser_forgetAPI_EME_forgetThisSite.js b/browser/components/contextualidentity/test/browser/browser_forgetAPI_EME_forgetThisSite.js
index dbcc7d194d225..910bfc589682f 100644
--- a/browser/components/contextualidentity/test/browser/browser_forgetAPI_EME_forgetThisSite.js
+++ b/browser/components/contextualidentity/test/browser/browser_forgetAPI_EME_forgetThisSite.js
@@ -199,7 +199,7 @@ async function checkEMEKey(browser, emeSessionId) {
 // Test functions.
 //
 
-add_task(async function setup() {
+add_setup(async function() {
   // Make sure userContext is enabled.
   await SpecialPowers.pushPrefEnv({
     set: [
diff --git a/browser/components/contextualidentity/test/browser/browser_forgetAPI_cookie_getCookiesWithOriginAttributes.js b/browser/components/contextualidentity/test/browser/browser_forgetAPI_cookie_getCookiesWithOriginAttributes.js
index 73c178c24e42a..960a5d886a98c 100644
--- a/browser/components/contextualidentity/test/browser/browser_forgetAPI_cookie_getCookiesWithOriginAttributes.js
+++ b/browser/components/contextualidentity/test/browser/browser_forgetAPI_cookie_getCookiesWithOriginAttributes.js
@@ -37,7 +37,7 @@ function getCookiesForOA(host, userContextId) {
 // Test functions.
 //
 
-add_task(async function setup() {
+add_setup(async function() {
   // Make sure userContext is enabled.
   await SpecialPowers.pushPrefEnv({
     set: [["privacy.userContext.enabled", true]],
diff --git a/browser/components/contextualidentity/test/browser/browser_forgetAPI_quota_clearStoragesForPrincipal.js b/browser/components/contextualidentity/test/browser/browser_forgetAPI_quota_clearStoragesForPrincipal.js
index ac1eee178b0bb..b749e73514d2c 100644
--- a/browser/components/contextualidentity/test/browser/browser_forgetAPI_quota_clearStoragesForPrincipal.js
+++ b/browser/components/contextualidentity/test/browser/browser_forgetAPI_quota_clearStoragesForPrincipal.js
@@ -107,7 +107,7 @@ async function checkIndexedDB(browser) {
 // Test functions.
 //
 
-add_task(async function setup() {
+add_setup(async function() {
   // Make sure userContext is enabled.
   await SpecialPowers.pushPrefEnv({
     set: [["privacy.userContext.enabled", true]],
diff --git a/browser/components/contextualidentity/test/browser/browser_forgetaboutsite.js b/browser/components/contextualidentity/test/browser/browser_forgetaboutsite.js
index b81200788ba8a..20c6653aa12b9 100644
--- a/browser/components/contextualidentity/test/browser/browser_forgetaboutsite.js
+++ b/browser/components/contextualidentity/test/browser/browser_forgetaboutsite.js
@@ -390,7 +390,7 @@ async function test_storage_cleared() {
   }
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // Make sure userContext is enabled.
   await SpecialPowers.pushPrefEnv({
     set: [["privacy.userContext.enabled", true]],
diff --git a/browser/components/contextualidentity/test/browser/browser_imageCache.js b/browser/components/contextualidentity/test/browser/browser_imageCache.js
index 77ebe8283e6ce..0c12907096e71 100644
--- a/browser/components/contextualidentity/test/browser/browser_imageCache.js
+++ b/browser/components/contextualidentity/test/browser/browser_imageCache.js
@@ -30,7 +30,7 @@ function fileHandler(metadata, response) {
   response.bodyOutputStream.write(body, body.length);
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // make sure userContext is enabled.
   await SpecialPowers.pushPrefEnv({
     set: [["privacy.userContext.enabled", true]],
diff --git a/browser/components/contextualidentity/test/browser/browser_originattrs_reopenin.js b/browser/components/contextualidentity/test/browser/browser_originattrs_reopenin.js
index 6b3555f26c1bf..777c0f010e5d5 100644
--- a/browser/components/contextualidentity/test/browser/browser_originattrs_reopenin.js
+++ b/browser/components/contextualidentity/test/browser/browser_originattrs_reopenin.js
@@ -34,7 +34,7 @@ function handleEventLocal(aEvent) {
   }
 }
 const NUM_PAGES_OPEN_FOR_EACH_TEST_CASE = 5;
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["privacy.userContext.enabled", true],
diff --git a/browser/components/contextualidentity/test/browser/browser_restore_getCookiesWithOriginAttributes.js b/browser/components/contextualidentity/test/browser/browser_restore_getCookiesWithOriginAttributes.js
index dda1d73cfb67a..6bb617094e5f0 100644
--- a/browser/components/contextualidentity/test/browser/browser_restore_getCookiesWithOriginAttributes.js
+++ b/browser/components/contextualidentity/test/browser/browser_restore_getCookiesWithOriginAttributes.js
@@ -40,7 +40,7 @@ function getCookiesForOA(host, userContextId) {
 // Test functions.
 //
 
-add_task(async function setup() {
+add_setup(async function() {
   // Make sure userContext is enabled.
   await SpecialPowers.pushPrefEnv({
     set: [["privacy.userContext.enabled", true]],
diff --git a/browser/components/contextualidentity/test/browser/browser_saveLink.js b/browser/components/contextualidentity/test/browser/browser_saveLink.js
index 94a8e748f9d67..d8df584d59888 100644
--- a/browser/components/contextualidentity/test/browser/browser_saveLink.js
+++ b/browser/components/contextualidentity/test/browser/browser_saveLink.js
@@ -8,7 +8,7 @@ const URI =
 let MockFilePicker = SpecialPowers.MockFilePicker;
 MockFilePicker.init(window);
 
-add_task(async function setup() {
+add_setup(async function() {
   info("Setting the prefs.");
 
   // make sure userContext is enabled.
diff --git a/browser/components/contextualidentity/test/browser/browser_serviceworkers.js b/browser/components/contextualidentity/test/browser/browser_serviceworkers.js
index cd7caff4a608e..763d2be7619a0 100644
--- a/browser/components/contextualidentity/test/browser/browser_serviceworkers.js
+++ b/browser/components/contextualidentity/test/browser/browser_serviceworkers.js
@@ -21,7 +21,7 @@ function openTabInUserContext(uri, userContextId) {
   return tab;
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // make sure userContext is enabled.
   await SpecialPowers.pushPrefEnv({
     set: [
diff --git a/browser/components/contextualidentity/test/browser/browser_usercontext.js b/browser/components/contextualidentity/test/browser/browser_usercontext.js
index 67869d25a1f90..79f7c2e6461d4 100644
--- a/browser/components/contextualidentity/test/browser/browser_usercontext.js
+++ b/browser/components/contextualidentity/test/browser/browser_usercontext.js
@@ -20,7 +20,7 @@ function openTabInUserContext(uri, userContextId) {
   return tab;
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // make sure userContext is enabled.
   await SpecialPowers.pushPrefEnv({
     set: [
diff --git a/browser/components/contextualidentity/test/browser/browser_usercontextid_new_window.js b/browser/components/contextualidentity/test/browser/browser_usercontextid_new_window.js
index 6c573bbc06435..b018a1f4c3fb1 100644
--- a/browser/components/contextualidentity/test/browser/browser_usercontextid_new_window.js
+++ b/browser/components/contextualidentity/test/browser/browser_usercontextid_new_window.js
@@ -52,7 +52,7 @@ function openWindowWithUserContextId(userContextId, isPrivate) {
   return windowPromise;
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["privacy.userContext.enabled", true]],
   });
diff --git a/browser/components/contextualidentity/test/browser/browser_windowName.js b/browser/components/contextualidentity/test/browser/browser_windowName.js
index 55ff0084fa5ac..71c003d2806e6 100644
--- a/browser/components/contextualidentity/test/browser/browser_windowName.js
+++ b/browser/components/contextualidentity/test/browser/browser_windowName.js
@@ -7,7 +7,7 @@ const BASE_URI =
   "http://mochi.test:8888/browser/browser/components/" +
   "contextualidentity/test/browser/empty_file.html";
 
-add_task(async function setup() {
+add_setup(async function() {
   // make sure userContext is enabled.
   await SpecialPowers.pushPrefEnv({
     set: [
diff --git a/browser/components/contextualidentity/test/browser/browser_windowOpen.js b/browser/components/contextualidentity/test/browser/browser_windowOpen.js
index d53f91cecc3fd..d28942506690c 100644
--- a/browser/components/contextualidentity/test/browser/browser_windowOpen.js
+++ b/browser/components/contextualidentity/test/browser/browser_windowOpen.js
@@ -7,7 +7,7 @@ const BASE_URI =
   "http://mochi.test:8888/browser/browser/components/" +
   "contextualidentity/test/browser/empty_file.html";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["privacy.userContext.enabled", true],
diff --git a/browser/components/customizableui/test/browser_PanelMultiView_focus.js b/browser/components/customizableui/test/browser_PanelMultiView_focus.js
index 7f088217ad825..8ea7131c2d0a6 100644
--- a/browser/components/customizableui/test/browser_PanelMultiView_focus.js
+++ b/browser/components/customizableui/test/browser_PanelMultiView_focus.js
@@ -20,7 +20,7 @@ let gMainSubButton;
 let gSubView;
 let gSubButton;
 
-add_task(async function setup() {
+add_setup(async function() {
   let navBar = document.getElementById("nav-bar");
   gAnchor = document.createXULElement("toolbarbutton");
   // Must be focusable in order for key presses to work.
diff --git a/browser/components/customizableui/test/browser_PanelMultiView_keyboard.js b/browser/components/customizableui/test/browser_PanelMultiView_keyboard.js
index 745acd6cb0459..fdfa943113b66 100644
--- a/browser/components/customizableui/test/browser_PanelMultiView_keyboard.js
+++ b/browser/components/customizableui/test/browser_PanelMultiView_keyboard.js
@@ -70,7 +70,7 @@ async function expectFocusAfterKey(aKey, aFocus) {
   ok(true, aFocus.id + " focused after " + aKey + " pressed");
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // This shouldn't be necessary - but it is, because we use same-process frames.
   // https://bugzilla.mozilla.org/show_bug.cgi?id=1565276 covers improving this.
   await SpecialPowers.pushPrefEnv({
diff --git a/browser/components/customizableui/test/browser_synced_tabs_menu.js b/browser/components/customizableui/test/browser_synced_tabs_menu.js
index 7d77f314704b4..a76762e13ce77 100644
--- a/browser/components/customizableui/test/browser_synced_tabs_menu.js
+++ b/browser/components/customizableui/test/browser_synced_tabs_menu.js
@@ -55,7 +55,7 @@ let mockedInternal = {
   hasSyncedThisSession: false,
 };
 
-add_task(async function setup() {
+add_setup(async function() {
   const getSignedInUser = FxAccounts.config.getSignedInUser;
   FxAccounts.config.getSignedInUser = async () =>
     Promise.resolve({ uid: "uid", email: "foo@bar.com" });
diff --git a/browser/components/downloads/test/browser/browser_download_overwrite.js b/browser/components/downloads/test/browser/browser_download_overwrite.js
index 53b23d7f1cd87..9e50a416f1f90 100644
--- a/browser/components/downloads/test/browser/browser_download_overwrite.js
+++ b/browser/components/downloads/test/browser/browser_download_overwrite.js
@@ -17,7 +17,7 @@ Services.scriptloader.loadSubScript(
   this
 );
 
-add_task(async function setup() {
+add_setup(async function() {
   // head.js has helpers that write to a nice unique file we can use.
   await createDownloadedFile(gTestTargetFile.path, "Hello.\n");
   ok(gTestTargetFile.exists(), "We created a test file.");
diff --git a/browser/components/downloads/test/browser/browser_download_spam_protection.js b/browser/components/downloads/test/browser/browser_download_spam_protection.js
index 8809b6a30bbda..e500e49878dcf 100644
--- a/browser/components/downloads/test/browser/browser_download_spam_protection.js
+++ b/browser/components/downloads/test/browser/browser_download_spam_protection.js
@@ -26,7 +26,7 @@ const TEST_PATH = getRootDirectory(gTestPath).replace(
   TEST_URI
 );
 
-add_task(async function setup() {
+add_setup(async function() {
   // Create temp directory
   let time = new Date().getTime();
   let tempDir = Services.dirsvc.get("TmpD", Ci.nsIFile);
diff --git a/browser/components/downloads/test/browser/browser_downloads_context_menu_always_open_similar_files.js b/browser/components/downloads/test/browser/browser_downloads_context_menu_always_open_similar_files.js
index 07fa8ebf524e1..2dcd72cf573e1 100644
--- a/browser/components/downloads/test/browser/browser_downloads_context_menu_always_open_similar_files.js
+++ b/browser/components/downloads/test/browser/browser_downloads_context_menu_always_open_similar_files.js
@@ -57,7 +57,7 @@ async function prepareDownloadFiles(downloadList) {
   info("Download target exists? " + download.target.exists);
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["browser.download.improvements_to_download_panel", true]],
   });
diff --git a/browser/components/downloads/test/browser/browser_downloads_panel_disable_items.js b/browser/components/downloads/test/browser/browser_downloads_panel_disable_items.js
index 1377a621522cc..88a3650718730 100644
--- a/browser/components/downloads/test/browser/browser_downloads_panel_disable_items.js
+++ b/browser/components/downloads/test/browser/browser_downloads_panel_disable_items.js
@@ -9,7 +9,7 @@ const TEST_PATH = getRootDirectory(gTestPath).replace(
   TEST_URI
 );
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.download.improvements_to_download_panel", true],
diff --git a/browser/components/downloads/test/browser/browser_downloads_panel_focus.js b/browser/components/downloads/test/browser/browser_downloads_panel_focus.js
index 1cd9f1679634f..68ec96335cf1c 100644
--- a/browser/components/downloads/test/browser/browser_downloads_panel_focus.js
+++ b/browser/components/downloads/test/browser/browser_downloads_panel_focus.js
@@ -3,7 +3,7 @@
 
 "use strict";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["browser.download.improvements_to_download_panel", true]],
   });
diff --git a/browser/components/downloads/test/browser/browser_library_clearall.js b/browser/components/downloads/test/browser/browser_library_clearall.js
index dea32e4ae3f8f..d4570cbc2535e 100644
--- a/browser/components/downloads/test/browser/browser_library_clearall.js
+++ b/browser/components/downloads/test/browser/browser_library_clearall.js
@@ -78,7 +78,7 @@ async function testClearingDownloads(clearCallback) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // Ensure that state is reset in case previous tests didn't finish.
   await task_resetState();
 
diff --git a/browser/components/downloads/test/browser/browser_library_select_all.js b/browser/components/downloads/test/browser/browser_library_select_all.js
index 779ccf337cf09..9944909bc5d0e 100644
--- a/browser/components/downloads/test/browser/browser_library_select_all.js
+++ b/browser/components/downloads/test/browser/browser_library_select_all.js
@@ -3,7 +3,7 @@
 
 let gDownloadDir;
 
-add_task(async function setup() {
+add_setup(async function() {
   await task_resetState();
 
   if (!gDownloadDir) {
diff --git a/browser/components/enterprisepolicies/tests/browser/browser_policy_block_set_desktop_background.js b/browser/components/enterprisepolicies/tests/browser/browser_policy_block_set_desktop_background.js
index d17a29a7b5223..ae67dbf2c2670 100644
--- a/browser/components/enterprisepolicies/tests/browser/browser_policy_block_set_desktop_background.js
+++ b/browser/components/enterprisepolicies/tests/browser/browser_policy_block_set_desktop_background.js
@@ -2,7 +2,7 @@
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 "use strict";
 
-add_task(async function setup() {
+add_setup(async function() {
   await setupPolicyEngineWithJson({
     policies: {
       DisableSetDesktopBackground: true,
diff --git a/browser/components/enterprisepolicies/tests/browser/browser_policy_disable_popup_blocker.js b/browser/components/enterprisepolicies/tests/browser/browser_policy_disable_popup_blocker.js
index 40075b98e6596..e6bac625704fc 100644
--- a/browser/components/enterprisepolicies/tests/browser/browser_policy_disable_popup_blocker.js
+++ b/browser/components/enterprisepolicies/tests/browser/browser_policy_disable_popup_blocker.js
@@ -7,7 +7,7 @@ function restore_prefs() {
 }
 
 let ORIGINAL_PREF_VALUE = undefined;
-add_task(async function setup() {
+add_setup(async function() {
   // It seems that this pref is given a special testing value for some reason.
   // Unset that value for this test, but save the old value
   if (Services.prefs.prefHasUserValue("dom.disable_open_during_load")) {
diff --git a/browser/components/enterprisepolicies/tests/browser/browser_policy_disable_privatebrowsing.js b/browser/components/enterprisepolicies/tests/browser/browser_policy_disable_privatebrowsing.js
index e8ce7e891a288..aeefa2e950a36 100644
--- a/browser/components/enterprisepolicies/tests/browser/browser_policy_disable_privatebrowsing.js
+++ b/browser/components/enterprisepolicies/tests/browser/browser_policy_disable_privatebrowsing.js
@@ -7,7 +7,7 @@ const { PrivateBrowsingUtils } = ChromeUtils.import(
   "resource://gre/modules/PrivateBrowsingUtils.jsm"
 );
 
-add_task(async function setup() {
+add_setup(async function() {
   await setupPolicyEngineWithJson({
     policies: {
       DisablePrivateBrowsing: true,
diff --git a/browser/components/enterprisepolicies/tests/browser/browser_policy_disable_profile_reset.js b/browser/components/enterprisepolicies/tests/browser/browser_policy_disable_profile_reset.js
index e3cb9f9c6872c..70a53872a1503 100644
--- a/browser/components/enterprisepolicies/tests/browser/browser_policy_disable_profile_reset.js
+++ b/browser/components/enterprisepolicies/tests/browser/browser_policy_disable_profile_reset.js
@@ -8,7 +8,7 @@ let { ResetProfile } = ChromeUtils.import(
 
 // For this test to work properly, this profile actually needs to be
 // "reset-able", which requires that it be recognized by the profile service
-add_task(async function setup() {
+add_setup(async function() {
   let profileDirectory = Services.dirsvc.get("ProfD", Ci.nsIFile);
   let profileName = profileDirectory.leafName;
   let profileService = Cc["@mozilla.org/toolkit/profile-service;1"].getService(
diff --git a/browser/components/enterprisepolicies/tests/browser/browser_policy_disable_safemode.js b/browser/components/enterprisepolicies/tests/browser/browser_policy_disable_safemode.js
index e6c8313cc6398..f1d1dd4fc4362 100644
--- a/browser/components/enterprisepolicies/tests/browser/browser_policy_disable_safemode.js
+++ b/browser/components/enterprisepolicies/tests/browser/browser_policy_disable_safemode.js
@@ -2,7 +2,7 @@
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 "use strict";
 
-add_task(async function setup() {
+add_setup(async function() {
   await setupPolicyEngineWithJson({
     policies: {
       DisableSafeMode: true,
diff --git a/browser/components/enterprisepolicies/tests/browser/browser_policy_display_bookmarks.js b/browser/components/enterprisepolicies/tests/browser/browser_policy_display_bookmarks.js
index effca803e0a27..d3c4e56ba31f3 100644
--- a/browser/components/enterprisepolicies/tests/browser/browser_policy_display_bookmarks.js
+++ b/browser/components/enterprisepolicies/tests/browser/browser_policy_display_bookmarks.js
@@ -3,7 +3,7 @@
 
 "use strict";
 
-add_task(async function setup() {
+add_setup(async function() {
   await setupPolicyEngineWithJson({
     policies: {
       DisplayBookmarksToolbar: true,
diff --git a/browser/components/enterprisepolicies/tests/browser/browser_policy_searchbar.js b/browser/components/enterprisepolicies/tests/browser/browser_policy_searchbar.js
index f4e16f26bb3bf..b04538931f53b 100644
--- a/browser/components/enterprisepolicies/tests/browser/browser_policy_searchbar.js
+++ b/browser/components/enterprisepolicies/tests/browser/browser_policy_searchbar.js
@@ -3,7 +3,7 @@
 
 "use strict";
 
-add_task(async function setup() {
+add_setup(async function() {
   await setupPolicyEngineWithJson({
     policies: {
       SearchBar: "separate",
@@ -23,7 +23,7 @@ add_task(async function test_menu_shown() {
   await BrowserTestUtils.closeWindow(newWin);
 });
 
-add_task(async function setup() {
+add_setup(async function() {
   await setupPolicyEngineWithJson({
     policies: {
       SearchBar: "unified",
diff --git a/browser/components/enterprisepolicies/tests/browser/browser_policy_set_startpage.js b/browser/components/enterprisepolicies/tests/browser/browser_policy_set_startpage.js
index 91c3184b36be3..36636b349491c 100644
--- a/browser/components/enterprisepolicies/tests/browser/browser_policy_set_startpage.js
+++ b/browser/components/enterprisepolicies/tests/browser/browser_policy_set_startpage.js
@@ -2,7 +2,7 @@
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 "use strict";
 
-add_task(async function setup() {
+add_setup(async function() {
   // browser.startup.page is set by unittest-required/user.js,
   // but we need the default value
   await SpecialPowers.pushPrefEnv({
diff --git a/browser/components/enterprisepolicies/tests/browser/browser_policy_support_menu.js b/browser/components/enterprisepolicies/tests/browser/browser_policy_support_menu.js
index 47139a0e32379..5f46ef24e4124 100644
--- a/browser/components/enterprisepolicies/tests/browser/browser_policy_support_menu.js
+++ b/browser/components/enterprisepolicies/tests/browser/browser_policy_support_menu.js
@@ -2,7 +2,7 @@
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 "use strict";
 
-add_task(async function setup() {
+add_setup(async function() {
   await setupPolicyEngineWithJson({
     policies: {
       SupportMenu: {
diff --git a/browser/components/extensions/test/browser/browser_ext_browserAction_simple.js b/browser/components/extensions/test/browser/browser_ext_browserAction_simple.js
index 316eb22da0acf..41770898a9e13 100644
--- a/browser/components/extensions/test/browser/browser_ext_browserAction_simple.js
+++ b/browser/components/extensions/test/browser/browser_ext_browserAction_simple.js
@@ -86,7 +86,7 @@ async function testAction(manifest_version) {
   await waitForConsole;
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["extensions.manifestV3.enabled", true]],
   });
diff --git a/browser/components/extensions/test/browser/browser_ext_menus_events.js b/browser/components/extensions/test/browser/browser_ext_menus_events.js
index 8a03a7886e075..4ae9e54545c6d 100644
--- a/browser/components/extensions/test/browser/browser_ext_menus_events.js
+++ b/browser/components/extensions/test/browser/browser_ext_menus_events.js
@@ -21,7 +21,7 @@ async function grantOptionalPermission(extension, permissions) {
 
 var someOtherTab, testTab;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["extensions.manifestV3.enabled", true]],
   });
diff --git a/browser/components/extensions/test/browser/browser_ext_pageAction_click_types.js b/browser/components/extensions/test/browser/browser_ext_pageAction_click_types.js
index dc101e06b2d4d..93c8be1d469f8 100644
--- a/browser/components/extensions/test/browser/browser_ext_pageAction_click_types.js
+++ b/browser/components/extensions/test/browser/browser_ext_pageAction_click_types.js
@@ -2,7 +2,7 @@
 /* vim: set sts=2 sw=2 et tw=80: */
 "use strict";
 
-add_task(async function setup() {
+add_setup(async function() {
   // The page action button is hidden by default.
   // This tests the use of pageAction when the button is visible.
   //
diff --git a/browser/components/extensions/test/browser/browser_ext_settings_overrides_default_search.js b/browser/components/extensions/test/browser/browser_ext_settings_overrides_default_search.js
index 79d10a5230d3d..9852994985701 100644
--- a/browser/components/extensions/test/browser/browser_ext_settings_overrides_default_search.js
+++ b/browser/components/extensions/test/browser/browser_ext_settings_overrides_default_search.js
@@ -33,7 +33,7 @@ async function restoreDefaultEngine() {
   await Services.search.setDefault(engine);
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   let searchExtensions = getChromeDir(getResolvedURI(gTestPath));
   searchExtensions.append("search-engines");
 
diff --git a/browser/components/extensions/test/browser/browser_ext_tabs_cookieStoreId.js b/browser/components/extensions/test/browser/browser_ext_tabs_cookieStoreId.js
index a5cd9dd9ca279..9cd276236c7b6 100644
--- a/browser/components/extensions/test/browser/browser_ext_tabs_cookieStoreId.js
+++ b/browser/components/extensions/test/browser/browser_ext_tabs_cookieStoreId.js
@@ -2,7 +2,7 @@
 /* vim: set sts=2 sw=2 et tw=80: */
 "use strict";
 
-add_task(async function setup() {
+add_setup(async function() {
   // make sure userContext is enabled.
   return SpecialPowers.pushPrefEnv({
     set: [["privacy.userContext.enabled", true]],
diff --git a/browser/components/extensions/test/browser/browser_ext_topSites.js b/browser/components/extensions/test/browser/browser_ext_topSites.js
index 60ae8ee024546..d64a9038e0e35 100644
--- a/browser/components/extensions/test/browser/browser_ext_topSites.js
+++ b/browser/components/extensions/test/browser/browser_ext_topSites.js
@@ -61,7 +61,7 @@ async function getSites(extension, options) {
   return extension.awaitMessage("sites");
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await PlacesUtils.history.clear();
   await PlacesUtils.bookmarks.eraseEverything();
 
diff --git a/browser/components/extensions/test/browser/browser_ext_webRequest.js b/browser/components/extensions/test/browser/browser_ext_webRequest.js
index 0feeee51a8c8e..9df48ebc1446e 100644
--- a/browser/components/extensions/test/browser/browser_ext_webRequest.js
+++ b/browser/components/extensions/test/browser/browser_ext_webRequest.js
@@ -65,7 +65,7 @@ let events = {
   onCompleted: [{ urls }, ["responseHeaders"]],
 };
 
-add_task(async function setup() {
+add_setup(async function() {
   extension = makeExtension(events);
   await extension.startup();
 });
diff --git a/browser/components/extensions/test/browser/browser_ext_webrtc.js b/browser/components/extensions/test/browser/browser_ext_webrtc.js
index f15c43d1e0b40..96f76ba21dd9a 100644
--- a/browser/components/extensions/test/browser/browser_ext_webrtc.js
+++ b/browser/components/extensions/test/browser/browser_ext_webrtc.js
@@ -4,7 +4,7 @@ const { PermissionTestUtils } = ChromeUtils.import(
   "resource://testing-common/PermissionTestUtils.jsm"
 );
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["media.navigator.permission.fake", true]],
   });
diff --git a/browser/components/newtab/test/browser/browser_aboutwelcome_multistage_default.js b/browser/components/newtab/test/browser/browser_aboutwelcome_multistage_default.js
index 486e6996314ba..731c50720204b 100644
--- a/browser/components/newtab/test/browser/browser_aboutwelcome_multistage_default.js
+++ b/browser/components/newtab/test/browser/browser_aboutwelcome_multistage_default.js
@@ -644,7 +644,7 @@ add_task(async function test_updatesPrefOnAWOpen() {
   Services.prefs.clearUserPref(DID_SEE_ABOUT_WELCOME_PREF);
 });
 
-add_task(async function setup() {
+add_setup(async function() {
   const sandbox = sinon.createSandbox();
   // This needs to happen before any about:welcome page opens
   sandbox.stub(FxAccounts.config, "promiseMetricsFlowURI").resolves("");
diff --git a/browser/components/newtab/test/browser/browser_asrouter_cfr.js b/browser/components/newtab/test/browser/browser_asrouter_cfr.js
index 5d9b4362cb0ca..b7bb46e1fe52b 100644
--- a/browser/components/newtab/test/browser/browser_asrouter_cfr.js
+++ b/browser/components/newtab/test/browser/browser_asrouter_cfr.js
@@ -178,7 +178,7 @@ function trigger_cfr_panel(
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // Store it in order to restore to the original value
   const { _fetchLatestAddonVersion } = CFRPageActions;
   // Prevent fetching the real addon url and making a network request
diff --git a/browser/components/newtab/test/browser/browser_asrouter_group_frequency.js b/browser/components/newtab/test/browser/browser_asrouter_group_frequency.js
index f6cef72e65f1b..a412979b16477 100644
--- a/browser/components/newtab/test/browser/browser_asrouter_group_frequency.js
+++ b/browser/components/newtab/test/browser/browser_asrouter_group_frequency.js
@@ -14,7 +14,7 @@ const { CFRPageActions } = ChromeUtils.import(
 /**
  * Load and modify a message for the test.
  */
-add_task(async function setup() {
+add_setup(async function() {
   const initialMsgCount = ASRouter.state.messages.length;
   const heartbeatMsg = (await CFRMessageProvider.getMessages()).find(
     m => m.id === "HEARTBEAT_TACTIC_2"
diff --git a/browser/components/newtab/test/browser/browser_asrouter_group_userprefs.js b/browser/components/newtab/test/browser/browser_asrouter_group_userprefs.js
index 172bfdb47c8c9..31a63dafabee8 100644
--- a/browser/components/newtab/test/browser/browser_asrouter_group_userprefs.js
+++ b/browser/components/newtab/test/browser/browser_asrouter_group_userprefs.js
@@ -14,7 +14,7 @@ const { CFRPageActions } = ChromeUtils.import(
 /**
  * Load and modify a message for the test.
  */
-add_task(async function setup() {
+add_setup(async function() {
   const initialMsgCount = ASRouter.state.messages.length;
   const heartbeatMsg = (await CFRMessageProvider.getMessages()).find(
     m => m.id === "HEARTBEAT_TACTIC_2"
diff --git a/browser/components/newtab/test/browser/browser_newtab_trigger.js b/browser/components/newtab/test/browser/browser_newtab_trigger.js
index cb58642d2b7d9..f3afe6eb89cac 100644
--- a/browser/components/newtab/test/browser/browser_newtab_trigger.js
+++ b/browser/components/newtab/test/browser/browser_newtab_trigger.js
@@ -9,7 +9,7 @@ const { ASRouter } = ChromeUtils.import(
 
 let sendTriggerMessageSpy;
 
-add_task(function setup() {
+add_setup(function() {
   let sandbox = sinon.createSandbox();
   sendTriggerMessageSpy = sandbox.spy(ASRouter, "sendTriggerMessage");
 
diff --git a/browser/components/newtab/test/browser/browser_trigger_listeners.js b/browser/components/newtab/test/browser/browser_trigger_listeners.js
index 02d4cb78b22ba..0d18cfb711844 100644
--- a/browser/components/newtab/test/browser/browser_trigger_listeners.js
+++ b/browser/components/newtab/test/browser/browser_trigger_listeners.js
@@ -2,7 +2,7 @@ const { ASRouterTriggerListeners } = ChromeUtils.import(
   "resource://activity-stream/lib/ASRouterTriggerListeners.jsm"
 );
 
-add_task(async function setup() {
+add_setup(async function() {
   registerCleanupFunction(() => {
     const trigger = ASRouterTriggerListeners.get("openURL");
     trigger.uninit();
diff --git a/browser/components/newtab/test/xpcshell/test_AboutHomeStartupCacheWorker.js b/browser/components/newtab/test/xpcshell/test_AboutHomeStartupCacheWorker.js
index 5b52e52426d77..116036ea30804 100644
--- a/browser/components/newtab/test/xpcshell/test_AboutHomeStartupCacheWorker.js
+++ b/browser/components/newtab/test/xpcshell/test_AboutHomeStartupCacheWorker.js
@@ -55,7 +55,7 @@ const NEWTAB_RENDER_URL =
  * a dynamic layout, and then have that layout point to a local feed rather
  * than one from the Pocket CDN.
  */
-add_task(async function setup() {
+add_setup(async function() {
   do_get_profile();
   // The SearchService is also needed in order to construct the initial state,
   // which means that the AddonManager needs to be available.
diff --git a/browser/components/originattributes/test/browser/browser_favicon_firstParty.js b/browser/components/originattributes/test/browser/browser_favicon_firstParty.js
index 40c8274796401..cd5bc824fd6b2 100644
--- a/browser/components/originattributes/test/browser/browser_favicon_firstParty.js
+++ b/browser/components/originattributes/test/browser/browser_favicon_firstParty.js
@@ -379,7 +379,7 @@ async function doTestForAllTabsFavicon(
   tabBrowser.removeAttribute("overflow");
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // Make sure first party isolation is enabled.
   await SpecialPowers.pushPrefEnv({
     set: [
diff --git a/browser/components/originattributes/test/browser/browser_favicon_userContextId.js b/browser/components/originattributes/test/browser/browser_favicon_userContextId.js
index ddde65e35d3a5..a53ebe296150d 100644
--- a/browser/components/originattributes/test/browser/browser_favicon_userContextId.js
+++ b/browser/components/originattributes/test/browser/browser_favicon_userContextId.js
@@ -328,7 +328,7 @@ async function doTestForAllTabsFavicon(aTestPage, aFaviconHost, aFaviconURL) {
   tabBrowser.removeAttribute("overflow");
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // Make sure userContext is enabled.
   await SpecialPowers.pushPrefEnv({
     set: [
diff --git a/browser/components/originattributes/test/browser/browser_firstPartyIsolation.js b/browser/components/originattributes/test/browser/browser_firstPartyIsolation.js
index a526d84a57978..471f4c77500ea 100644
--- a/browser/components/originattributes/test/browser/browser_firstPartyIsolation.js
+++ b/browser/components/originattributes/test/browser/browser_firstPartyIsolation.js
@@ -3,7 +3,7 @@ const BASE_URL =
 const EXAMPLE_BASE_URL = BASE_URL.replace("mochi.test:8888", "example.com");
 const BASE_DOMAIN = "mochi.test";
 
-add_task(async function setup() {
+add_setup(async function() {
   Services.prefs.setBoolPref("privacy.firstparty.isolate", true);
   Services.prefs.setBoolPref("dom.security.https_first", false);
   registerCleanupFunction(function() {
diff --git a/browser/components/originattributes/test/browser/browser_firstPartyIsolation_aboutPages.js b/browser/components/originattributes/test/browser/browser_firstPartyIsolation_aboutPages.js
index c17ef66af1da4..f9256440061ca 100644
--- a/browser/components/originattributes/test/browser/browser_firstPartyIsolation_aboutPages.js
+++ b/browser/components/originattributes/test/browser/browser_firstPartyIsolation_aboutPages.js
@@ -2,7 +2,7 @@ if (SpecialPowers.useRemoteSubframes) {
   requestLongerTimeout(2);
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   Services.prefs.setBoolPref("privacy.firstparty.isolate", true);
   // Bug 1617611: Fix all the tests broken by "cookies SameSite=lax by default"
   Services.prefs.setBoolPref("network.cookie.sameSite.laxByDefault", false);
diff --git a/browser/components/originattributes/test/browser/browser_firstPartyIsolation_about_newtab.js b/browser/components/originattributes/test/browser/browser_firstPartyIsolation_about_newtab.js
index a861a1c06f92e..ccb52fa96f37c 100644
--- a/browser/components/originattributes/test/browser/browser_firstPartyIsolation_about_newtab.js
+++ b/browser/components/originattributes/test/browser/browser_firstPartyIsolation_about_newtab.js
@@ -1,4 +1,4 @@
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.newtab.preload", false],
diff --git a/browser/components/originattributes/test/browser/browser_firstPartyIsolation_blobURI.js b/browser/components/originattributes/test/browser/browser_firstPartyIsolation_blobURI.js
index bfe85f3416ba6..4e19f8fe6ad13 100644
--- a/browser/components/originattributes/test/browser/browser_firstPartyIsolation_blobURI.js
+++ b/browser/components/originattributes/test/browser/browser_firstPartyIsolation_blobURI.js
@@ -1,4 +1,4 @@
-add_task(async function setup() {
+add_setup(async function() {
   Services.prefs.setBoolPref("privacy.firstparty.isolate", true);
 
   registerCleanupFunction(function() {
diff --git a/browser/components/originattributes/test/browser/browser_firstPartyIsolation_js_uri.js b/browser/components/originattributes/test/browser/browser_firstPartyIsolation_js_uri.js
index 3ffc6d55ac328..2b44e21c6db1a 100644
--- a/browser/components/originattributes/test/browser/browser_firstPartyIsolation_js_uri.js
+++ b/browser/components/originattributes/test/browser/browser_firstPartyIsolation_js_uri.js
@@ -1,4 +1,4 @@
-add_task(async function setup() {
+add_setup(async function() {
   Services.prefs.setBoolPref("privacy.firstparty.isolate", true);
 
   registerCleanupFunction(function() {
diff --git a/browser/components/originattributes/test/browser/browser_firstPartyIsolation_saveAs.js b/browser/components/originattributes/test/browser/browser_firstPartyIsolation_saveAs.js
index e229aa6a76ac4..ec8ba9cbfd86c 100644
--- a/browser/components/originattributes/test/browser/browser_firstPartyIsolation_saveAs.js
+++ b/browser/components/originattributes/test/browser/browser_firstPartyIsolation_saveAs.js
@@ -32,7 +32,7 @@ MockFilePicker.init(window);
 const tempDir = createTemporarySaveDirectory();
 MockFilePicker.displayDirectory = tempDir;
 
-add_task(async function setup() {
+add_setup(async function() {
   info("Setting the prefs.");
 
   await SpecialPowers.pushPrefEnv({
diff --git a/browser/components/originattributes/test/browser/browser_postMessage.js b/browser/components/originattributes/test/browser/browser_postMessage.js
index e8860bd94b0d9..9cfe8c44a293f 100644
--- a/browser/components/originattributes/test/browser/browser_postMessage.js
+++ b/browser/components/originattributes/test/browser/browser_postMessage.js
@@ -7,7 +7,7 @@ const FPD_TWO = "http://example.org";
 
 const TEST_BASE = "/browser/browser/components/originattributes/test/browser/";
 
-add_task(async function setup() {
+add_setup(async function() {
   // Make sure first party isolation is enabled.
   await SpecialPowers.pushPrefEnv({
     set: [
diff --git a/browser/components/originattributes/test/browser/browser_sanitize.js b/browser/components/originattributes/test/browser/browser_sanitize.js
index 8f83f2309bcc9..625dd85c65230 100644
--- a/browser/components/originattributes/test/browser/browser_sanitize.js
+++ b/browser/components/originattributes/test/browser/browser_sanitize.js
@@ -77,7 +77,7 @@ function checkCacheExists(aShouldExist) {
   };
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   Services.cache2.clear();
 });
 
diff --git a/browser/components/places/tests/browser/browser_autoshow_bookmarks_toolbar.js b/browser/components/places/tests/browser/browser_autoshow_bookmarks_toolbar.js
index 8f2c7a4a65fee..81394ca3edea4 100644
--- a/browser/components/places/tests/browser/browser_autoshow_bookmarks_toolbar.js
+++ b/browser/components/places/tests/browser/browser_autoshow_bookmarks_toolbar.js
@@ -8,7 +8,7 @@ const TOOLBAR_VISIBILITY_PREF = "browser.toolbars.bookmarks.visibility";
 let bookmarkPanel;
 let win;
 
-add_task(async function setup() {
+add_setup(async function() {
   Services.prefs.clearUserPref(LOCATION_PREF);
   await PlacesUtils.bookmarks.eraseEverything();
 
diff --git a/browser/components/places/tests/browser/browser_bookmarkMenu_hiddenWindow.js b/browser/components/places/tests/browser/browser_bookmarkMenu_hiddenWindow.js
index 4473a01119c02..f897092e93fb6 100644
--- a/browser/components/places/tests/browser/browser_bookmarkMenu_hiddenWindow.js
+++ b/browser/components/places/tests/browser/browser_bookmarkMenu_hiddenWindow.js
@@ -4,7 +4,7 @@
 
 "use strict";
 
-add_task(async function setup() {
+add_setup(async function() {
   await PlacesUtils.bookmarks.insert({
     parentGuid: PlacesUtils.bookmarks.menuGuid,
     url: "http://example.com/",
diff --git a/browser/components/places/tests/browser/browser_bookmarkProperties_cancel.js b/browser/components/places/tests/browser/browser_bookmarkProperties_cancel.js
index f4362d2a11160..e178875e932cd 100644
--- a/browser/components/places/tests/browser/browser_bookmarkProperties_cancel.js
+++ b/browser/components/places/tests/browser/browser_bookmarkProperties_cancel.js
@@ -12,7 +12,7 @@ registerCleanupFunction(async function() {
 
 let bookmarks; // Bookmarks added via insertTree.
 
-add_task(async function setup() {
+add_setup(async function() {
   bookmarks = await PlacesUtils.bookmarks.insertTree({
     guid: PlacesUtils.bookmarks.unfiledGuid,
     children: [
diff --git a/browser/components/places/tests/browser/browser_bookmarkProperties_folderSelection.js b/browser/components/places/tests/browser/browser_bookmarkProperties_folderSelection.js
index 0c22002e00ebf..9e07a07396e06 100644
--- a/browser/components/places/tests/browser/browser_bookmarkProperties_folderSelection.js
+++ b/browser/components/places/tests/browser/browser_bookmarkProperties_folderSelection.js
@@ -7,7 +7,7 @@ let bookmarkPanel;
 let folders;
 let win;
 
-add_task(async function setup() {
+add_setup(async function() {
   await PlacesUtils.bookmarks.eraseEverything();
 
   Services.prefs.clearUserPref("browser.bookmarks.defaultLocation");
diff --git a/browser/components/places/tests/browser/browser_bookmarkProperties_newFolder.js b/browser/components/places/tests/browser/browser_bookmarkProperties_newFolder.js
index cd12522606049..b08a39fad8962 100644
--- a/browser/components/places/tests/browser/browser_bookmarkProperties_newFolder.js
+++ b/browser/components/places/tests/browser/browser_bookmarkProperties_newFolder.js
@@ -7,7 +7,7 @@ StarUI._createPanelIfNeeded();
 const bookmarkPanel = document.getElementById("editBookmarkPanel");
 let folders;
 
-add_task(async function setup() {
+add_setup(async function() {
   await PlacesUtils.bookmarks.eraseEverything();
 
   bookmarkPanel.setAttribute("animate", false);
diff --git a/browser/components/places/tests/browser/browser_bookmarkProperties_remember_folders.js b/browser/components/places/tests/browser/browser_bookmarkProperties_remember_folders.js
index 82ffe56bdd8c3..716aca1e5b61a 100644
--- a/browser/components/places/tests/browser/browser_bookmarkProperties_remember_folders.js
+++ b/browser/components/places/tests/browser/browser_bookmarkProperties_remember_folders.js
@@ -84,7 +84,7 @@ async function assertRecentFolders(expectedGuids, msg) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await PlacesUtils.bookmarks.eraseEverything();
   await PlacesUtils.metadata.delete(PlacesUIUtils.LAST_USED_FOLDERS_META_KEY);
 
diff --git a/browser/components/places/tests/browser/browser_bookmarkProperties_speculativeConnection.js b/browser/components/places/tests/browser/browser_bookmarkProperties_speculativeConnection.js
index d590991a7026b..342e12c71d5b7 100644
--- a/browser/components/places/tests/browser/browser_bookmarkProperties_speculativeConnection.js
+++ b/browser/components/places/tests/browser/browser_bookmarkProperties_speculativeConnection.js
@@ -13,7 +13,7 @@ let spy = sandbox
   .stub(PlacesUIUtils, "setupSpeculativeConnection")
   .returns(Promise.resolve());
 
-add_task(async function setup() {
+add_setup(async function() {
   await PlacesUtils.bookmarks.eraseEverything();
 
   let toolbar = document.getElementById("PersonalToolbar");
diff --git a/browser/components/places/tests/browser/browser_bookmark_add_tags.js b/browser/components/places/tests/browser/browser_bookmark_add_tags.js
index 36d2c0d6dc678..e09cd7c88f863 100644
--- a/browser/components/places/tests/browser/browser_bookmark_add_tags.js
+++ b/browser/components/places/tests/browser/browser_bookmark_add_tags.js
@@ -24,7 +24,7 @@ async function hideBookmarksPanel(callback) {
   await hiddenPromise;
 }
 
-add_task(function setup() {
+add_setup(function() {
   let oldTimeout = StarUI._autoCloseTimeout;
 
   bookmarkPanel.setAttribute("animate", false);
diff --git a/browser/components/places/tests/browser/browser_bookmark_backup_export_import.js b/browser/components/places/tests/browser/browser_bookmark_backup_export_import.js
index 5a1eeefde3c76..d50019cf383f8 100644
--- a/browser/components/places/tests/browser/browser_bookmark_backup_export_import.js
+++ b/browser/components/places/tests/browser/browser_bookmark_backup_export_import.js
@@ -113,7 +113,7 @@ async function promiseImportExport(aWindow) {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await promisePlacesInitComplete();
   await PlacesUtils.bookmarks.eraseEverything();
   await generateTestBookmarks();
diff --git a/browser/components/places/tests/browser/browser_bookmark_change_location.js b/browser/components/places/tests/browser/browser_bookmark_change_location.js
index a5808157708be..da133004a1d9a 100644
--- a/browser/components/places/tests/browser/browser_bookmark_change_location.js
+++ b/browser/components/places/tests/browser/browser_bookmark_change_location.js
@@ -12,7 +12,7 @@ const TEST_URL2 = "about:config";
 const TEST_URL3 = "about:credits";
 
 // Setup.
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["browser.toolbars.bookmarks.visibility", "always"]],
   });
diff --git a/browser/components/places/tests/browser/browser_bookmark_context_menu_contents.js b/browser/components/places/tests/browser/browser_bookmark_context_menu_contents.js
index 37e847fab68b1..fdd6d4c81233a 100644
--- a/browser/components/places/tests/browser/browser_bookmark_context_menu_contents.js
+++ b/browser/components/places/tests/browser/browser_bookmark_context_menu_contents.js
@@ -24,7 +24,7 @@ const bookmarksInfo = [
 ];
 const TEST_URL = "about:mozilla";
 
-add_task(async function setup() {
+add_setup(async function() {
   await PlacesUtils.bookmarks.eraseEverything();
 
   let toolbar = document.getElementById("PersonalToolbar");
diff --git a/browser/components/places/tests/browser/browser_bookmark_popup.js b/browser/components/places/tests/browser/browser_bookmark_popup.js
index c2dc804cdb446..a7b9a8b137b5e 100644
--- a/browser/components/places/tests/browser/browser_bookmark_popup.js
+++ b/browser/components/places/tests/browser/browser_bookmark_popup.js
@@ -22,7 +22,7 @@ const TEST_URL = "data:text/html,<html><body></body></html>";
 
 StarUI._closePanelQuickForTesting = true;
 
-add_task(async function setup() {
+add_setup(async function() {
   bookmarkPanel.setAttribute("animate", false);
   registerCleanupFunction(() => {
     bookmarkPanel.removeAttribute("animate");
diff --git a/browser/components/places/tests/browser/browser_bookmark_remove_tags.js b/browser/components/places/tests/browser/browser_bookmark_remove_tags.js
index fce4a8e923c56..af85e5c7f47a4 100644
--- a/browser/components/places/tests/browser/browser_bookmark_remove_tags.js
+++ b/browser/components/places/tests/browser/browser_bookmark_remove_tags.js
@@ -7,7 +7,7 @@ const TEST_URL = "about:buildconfig";
 const TEST_URI = Services.io.newURI(TEST_URL);
 
 // Setup.
-add_task(async function setup() {
+add_setup(async function() {
   let toolbar = document.getElementById("PersonalToolbar");
   let wasCollapsed = toolbar.collapsed;
 
diff --git a/browser/components/places/tests/browser/browser_bookmarks_change_title.js b/browser/components/places/tests/browser/browser_bookmarks_change_title.js
index dcf82a37206e3..a6361f33d5057 100644
--- a/browser/components/places/tests/browser/browser_bookmarks_change_title.js
+++ b/browser/components/places/tests/browser/browser_bookmarks_change_title.js
@@ -17,7 +17,7 @@ function getToolbarNodeForItemGuid(aItemGuid) {
 }
 
 // Setup.
-add_task(async function setup() {
+add_setup(async function() {
   let toolbar = document.getElementById("PersonalToolbar");
   let wasCollapsed = toolbar.collapsed;
 
diff --git a/browser/components/places/tests/browser/browser_click_bookmarks_on_toolbar.js b/browser/components/places/tests/browser/browser_click_bookmarks_on_toolbar.js
index 468cbb932ef63..b4f4b07b63758 100644
--- a/browser/components/places/tests/browser/browser_click_bookmarks_on_toolbar.js
+++ b/browser/components/places/tests/browser/browser_click_bookmarks_on_toolbar.js
@@ -65,7 +65,7 @@ function waitForNewTab(url, inBackground) {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await PlacesUtils.bookmarks.eraseEverything();
   let bookmarks = await Promise.all(
     TEST_PAGES.map((url, index) => {
diff --git a/browser/components/places/tests/browser/browser_controller_onDrop.js b/browser/components/places/tests/browser/browser_controller_onDrop.js
index 6f51b670daf9f..7197c0c6420c4 100644
--- a/browser/components/places/tests/browser/browser_controller_onDrop.js
+++ b/browser/components/places/tests/browser/browser_controller_onDrop.js
@@ -8,7 +8,7 @@ var bookmarks;
 var bookmarkIds;
 var library;
 
-add_task(async function setup() {
+add_setup(async function() {
   registerCleanupFunction(async function() {
     await PlacesUtils.bookmarks.eraseEverything();
     await PlacesUtils.history.clear();
diff --git a/browser/components/places/tests/browser/browser_controller_onDrop_query.js b/browser/components/places/tests/browser/browser_controller_onDrop_query.js
index ed3604e0104e8..212e5940e60a5 100644
--- a/browser/components/places/tests/browser/browser_controller_onDrop_query.js
+++ b/browser/components/places/tests/browser/browser_controller_onDrop_query.js
@@ -5,7 +5,7 @@
 
 const TEST_URL = "about:buildconfig";
 
-add_task(async function setup() {
+add_setup(async function() {
   // Clean before and after so we don't have anything in the folders.
   await PlacesUtils.bookmarks.eraseEverything();
 
diff --git a/browser/components/places/tests/browser/browser_controller_onDrop_sidebar.js b/browser/components/places/tests/browser/browser_controller_onDrop_sidebar.js
index 79c12c47abe73..ebf7d1b1e9760 100644
--- a/browser/components/places/tests/browser/browser_controller_onDrop_sidebar.js
+++ b/browser/components/places/tests/browser/browser_controller_onDrop_sidebar.js
@@ -5,7 +5,7 @@
 
 const TEST_URL = "about:buildconfig";
 
-add_task(async function setup() {
+add_setup(async function() {
   // Clean before and after so we don't have anything in the folders.
   await PlacesUtils.bookmarks.eraseEverything();
 
diff --git a/browser/components/places/tests/browser/browser_controller_onDrop_tagFolder.js b/browser/components/places/tests/browser/browser_controller_onDrop_tagFolder.js
index 199dda25d8e86..c138c3a783888 100644
--- a/browser/components/places/tests/browser/browser_controller_onDrop_tagFolder.js
+++ b/browser/components/places/tests/browser/browser_controller_onDrop_tagFolder.js
@@ -12,7 +12,7 @@ const TAG_NAME = "testTag";
 var bookmarks;
 var bookmarkId;
 
-add_task(async function setup() {
+add_setup(async function() {
   registerCleanupFunction(async function() {
     sandbox.restore();
     await PlacesUtils.bookmarks.eraseEverything();
diff --git a/browser/components/places/tests/browser/browser_default_bookmark_location.js b/browser/components/places/tests/browser/browser_default_bookmark_location.js
index 16ec05e7cceef..247603b776af9 100644
--- a/browser/components/places/tests/browser/browser_default_bookmark_location.js
+++ b/browser/components/places/tests/browser/browser_default_bookmark_location.js
@@ -8,7 +8,7 @@ const TEST_URL = "about:about";
 let bookmarkPanel;
 let win;
 
-add_task(async function setup() {
+add_setup(async function() {
   Services.prefs.clearUserPref(LOCATION_PREF);
   await PlacesUtils.bookmarks.eraseEverything();
 
diff --git a/browser/components/places/tests/browser/browser_drag_bookmarks_on_toolbar.js b/browser/components/places/tests/browser/browser_drag_bookmarks_on_toolbar.js
index a4bd3686bea64..4607cad5658c8 100644
--- a/browser/components/places/tests/browser/browser_drag_bookmarks_on_toolbar.js
+++ b/browser/components/places/tests/browser/browser_drag_bookmarks_on_toolbar.js
@@ -167,7 +167,7 @@ function getExpectedDataForPlacesNode(aNode) {
   return [wrappedNode];
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   var toolbar = document.getElementById("PersonalToolbar");
   var wasCollapsed = toolbar.collapsed;
 
diff --git a/browser/components/places/tests/browser/browser_drag_folder_on_newTab.js b/browser/components/places/tests/browser/browser_drag_folder_on_newTab.js
index 5179d7c2435c9..beefae9e8d300 100644
--- a/browser/components/places/tests/browser/browser_drag_folder_on_newTab.js
+++ b/browser/components/places/tests/browser/browser_drag_folder_on_newTab.js
@@ -3,7 +3,7 @@
 
 "use strict";
 
-add_task(async function setup() {
+add_setup(async function() {
   let toolbar = document.getElementById("PersonalToolbar");
   let wasCollapsed = toolbar.collapsed;
 
diff --git a/browser/components/places/tests/browser/browser_library_bookmark_pages.js b/browser/components/places/tests/browser/browser_library_bookmark_pages.js
index 7c9139af35394..9dfc180541678 100644
--- a/browser/components/places/tests/browser/browser_library_bookmark_pages.js
+++ b/browser/components/places/tests/browser/browser_library_bookmark_pages.js
@@ -11,7 +11,7 @@
 const TEST_URIS = ["https://example1.com/", "https://example2.com/"];
 let library;
 
-add_task(async function setup() {
+add_setup(async function() {
   await PlacesTestUtils.addVisits(TEST_URIS);
 
   library = await promiseLibrary("History");
diff --git a/browser/components/places/tests/browser/browser_library_openFlatContainer.js b/browser/components/places/tests/browser/browser_library_openFlatContainer.js
index 5e56c7179da29..3847325682d01 100644
--- a/browser/components/places/tests/browser/browser_library_openFlatContainer.js
+++ b/browser/components/places/tests/browser/browser_library_openFlatContainer.js
@@ -9,7 +9,7 @@
 
 var library;
 
-add_task(async function setup() {
+add_setup(async function() {
   await PlacesUtils.bookmarks.eraseEverything();
   await PlacesUtils.history.clear();
 
diff --git a/browser/components/places/tests/browser/browser_library_open_all.js b/browser/components/places/tests/browser/browser_library_open_all.js
index 5443e0346d6ff..dcb95405ce0c7 100644
--- a/browser/components/places/tests/browser/browser_library_open_all.js
+++ b/browser/components/places/tests/browser/browser_library_open_all.js
@@ -2,7 +2,7 @@
  * http://creativecommons.org/publicdomain/zero/1.0/
  */
 
-add_task(async function setup() {
+add_setup(async function() {
   await PlacesUtils.bookmarks.eraseEverything();
   const TEST_EXAMPLE_URL = "http://example.com/";
   const TEST_EXAMPLE_PARAMS = "?foo=1|2";
diff --git a/browser/components/places/tests/browser/browser_library_open_all_with_separator.js b/browser/components/places/tests/browser/browser_library_open_all_with_separator.js
index 32cdacdefea5a..6afbeec0bc074 100644
--- a/browser/components/places/tests/browser/browser_library_open_all_with_separator.js
+++ b/browser/components/places/tests/browser/browser_library_open_all_with_separator.js
@@ -2,7 +2,7 @@
  * http://creativecommons.org/publicdomain/zero/1.0/
  */
 
-add_task(async function setup() {
+add_setup(async function() {
   await PlacesUtils.bookmarks.eraseEverything();
 
   await PlacesUtils.bookmarks.insertTree({
diff --git a/browser/components/places/tests/browser/browser_library_views_liveupdate.js b/browser/components/places/tests/browser/browser_library_views_liveupdate.js
index d05565804f439..e4483785075e7 100644
--- a/browser/components/places/tests/browser/browser_library_views_liveupdate.js
+++ b/browser/components/places/tests/browser/browser_library_views_liveupdate.js
@@ -8,7 +8,7 @@
 
 let gLibrary = null;
 
-add_task(async function setup() {
+add_setup(async function() {
   gLibrary = await promiseLibrary();
 
   await PlacesUtils.bookmarks.eraseEverything();
diff --git a/browser/components/places/tests/browser/browser_library_warnOnOpen.js b/browser/components/places/tests/browser/browser_library_warnOnOpen.js
index d53c6b167e9ba..323765163f73f 100644
--- a/browser/components/places/tests/browser/browser_library_warnOnOpen.js
+++ b/browser/components/places/tests/browser/browser_library_warnOnOpen.js
@@ -10,7 +10,7 @@
 
 var gLibrary = null;
 
-add_task(async function setup() {
+add_setup(async function() {
   // Temporarily disable history, so we won't record pages navigation.
   await SpecialPowers.pushPrefEnv({ set: [["places.history.enabled", false]] });
 
diff --git a/browser/components/places/tests/browser/browser_paste_bookmarks.js b/browser/components/places/tests/browser/browser_paste_bookmarks.js
index e7155a121861c..12fd97bc73154 100644
--- a/browser/components/places/tests/browser/browser_paste_bookmarks.js
+++ b/browser/components/places/tests/browser/browser_paste_bookmarks.js
@@ -9,7 +9,7 @@ const TEST_URL1 = "https://example.com/otherbrowser/";
 var PlacesOrganizer;
 var ContentTree;
 
-add_task(async function setup() {
+add_setup(async function() {
   await PlacesUtils.bookmarks.eraseEverything();
   let organizer = await promiseLibrary();
 
diff --git a/browser/components/places/tests/browser/browser_paste_resets_cut_highlights.js b/browser/components/places/tests/browser/browser_paste_resets_cut_highlights.js
index f6636f63a0df8..6efaedfdff7e5 100644
--- a/browser/components/places/tests/browser/browser_paste_resets_cut_highlights.js
+++ b/browser/components/places/tests/browser/browser_paste_resets_cut_highlights.js
@@ -9,7 +9,7 @@ const TEST_URL1 = "https://example.com/otherbrowser/";
 var PlacesOrganizer;
 var ContentTree;
 
-add_task(async function setup() {
+add_setup(async function() {
   await PlacesUtils.bookmarks.eraseEverything();
   let organizer = await promiseLibrary();
 
diff --git a/browser/components/places/tests/browser/browser_remove_bookmarks.js b/browser/components/places/tests/browser/browser_remove_bookmarks.js
index bf81440a673db..2b2bbcff61bb3 100644
--- a/browser/components/places/tests/browser/browser_remove_bookmarks.js
+++ b/browser/components/places/tests/browser/browser_remove_bookmarks.js
@@ -10,7 +10,7 @@
 
 const TEST_URL = "about:mozilla";
 
-add_task(async function setup() {
+add_setup(async function() {
   await PlacesUtils.bookmarks.eraseEverything();
 
   let toolbar = document.getElementById("PersonalToolbar");
diff --git a/browser/components/places/tests/browser/browser_sidebar_open_bookmarks.js b/browser/components/places/tests/browser/browser_sidebar_open_bookmarks.js
index 85ca2f07770ca..41af88985eab9 100644
--- a/browser/components/places/tests/browser/browser_sidebar_open_bookmarks.js
+++ b/browser/components/places/tests/browser/browser_sidebar_open_bookmarks.js
@@ -7,7 +7,7 @@ const PREF_LOAD_BOOKMARKS_IN_TABS = "browser.tabs.loadBookmarksInTabs";
 
 var gBms;
 
-add_task(async function setup() {
+add_setup(async function() {
   gBms = await PlacesUtils.bookmarks.insertTree({
     guid: PlacesUtils.bookmarks.unfiledGuid,
     children: [
diff --git a/browser/components/places/tests/browser/browser_toolbar_library_open_recent.js b/browser/components/places/tests/browser/browser_toolbar_library_open_recent.js
index 12fc49fcaf29a..cffe9feafa08d 100644
--- a/browser/components/places/tests/browser/browser_toolbar_library_open_recent.js
+++ b/browser/components/places/tests/browser/browser_toolbar_library_open_recent.js
@@ -122,7 +122,7 @@ async function getRecentlyBookmarkedItems() {
   return Array.from(items).slice(0, 2);
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   let libraryButton = CustomizableUI.getPlacementOfWidget("library-button");
   if (!libraryButton) {
     CustomizableUI.addWidgetToArea(
diff --git a/browser/components/places/tests/browser/browser_toolbar_other_bookmarks.js b/browser/components/places/tests/browser/browser_toolbar_other_bookmarks.js
index 6147f7cd0386b..d09724f387b25 100644
--- a/browser/components/places/tests/browser/browser_toolbar_other_bookmarks.js
+++ b/browser/components/places/tests/browser/browser_toolbar_other_bookmarks.js
@@ -25,7 +25,7 @@ const bookmarksInfo = [
  */
 
 // Setup.
-add_task(async function setup() {
+add_setup(async function() {
   let toolbar = document.getElementById("PersonalToolbar");
   let wasCollapsed = toolbar.collapsed;
 
diff --git a/browser/components/places/tests/browser/browser_toolbar_overflow.js b/browser/components/places/tests/browser/browser_toolbar_overflow.js
index 028b1a99f6d27..82612171756e0 100644
--- a/browser/components/places/tests/browser/browser_toolbar_overflow.js
+++ b/browser/components/places/tests/browser/browser_toolbar_overflow.js
@@ -11,7 +11,7 @@ var gChevron = document.getElementById("PlacesChevron");
 
 const BOOKMARKS_COUNT = 250;
 
-add_task(async function setup() {
+add_setup(async function() {
   let wasCollapsed = gToolbar.collapsed;
   await PlacesUtils.bookmarks.eraseEverything();
 
diff --git a/browser/components/places/tests/browser/interactions/browser_interactions_blocklist.js b/browser/components/places/tests/browser/interactions/browser_interactions_blocklist.js
index d905522a5a0e3..5bd8c6fcc172e 100644
--- a/browser/components/places/tests/browser/interactions/browser_interactions_blocklist.js
+++ b/browser/components/places/tests/browser/interactions/browser_interactions_blocklist.js
@@ -13,7 +13,7 @@ XPCOMUtils.defineLazyModuleGetters(this, {
   InteractionsBlocklist: "resource:///modules/InteractionsBlocklist.jsm",
 });
 
-add_task(async function setup() {
+add_setup(async function() {
   let oldBlocklistValue = Services.prefs.getStringPref(
     "places.interactions.customBlocklist",
     "[]"
diff --git a/browser/components/preferences/tests/browser_applications_selection.js b/browser/components/preferences/tests/browser_applications_selection.js
index 9c5093a118e13..0ae5985b3e55d 100644
--- a/browser/components/preferences/tests/browser_applications_selection.js
+++ b/browser/components/preferences/tests/browser_applications_selection.js
@@ -65,7 +65,7 @@ function scrubMailtoHandlers(handlerInfo) {
   }
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // Create our dummy handlers
   let handler1 = Cc["@mozilla.org/uriloader/web-handler-app;1"].createInstance(
     Ci.nsIWebHandlerApp
diff --git a/browser/components/preferences/tests/browser_cloud_storage.js b/browser/components/preferences/tests/browser_cloud_storage.js
index 038496ede71de..3d6b57c5d4856 100644
--- a/browser/components/preferences/tests/browser_cloud_storage.js
+++ b/browser/components/preferences/tests/browser_cloud_storage.js
@@ -76,7 +76,7 @@ async function mock_dropbox() {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // Create mock Dropbox download folder for cloudstorage API
   // Set prefs required to display second radio option
   // 'Save to Dropbox' under Downloads
diff --git a/browser/components/preferences/tests/browser_containers_name_input.js b/browser/components/preferences/tests/browser_containers_name_input.js
index a59ea35b19301..b456c693f851d 100644
--- a/browser/components/preferences/tests/browser_containers_name_input.js
+++ b/browser/components/preferences/tests/browser_containers_name_input.js
@@ -1,7 +1,7 @@
 const CONTAINERS_URL =
   "chrome://browser/content/preferences/dialogs/containers.xhtml";
 
-add_task(async function setup() {
+add_setup(async function() {
   await openPreferencesViaOpenPreferencesAPI("containers", { leaveOpen: true });
   registerCleanupFunction(async function() {
     BrowserTestUtils.removeTab(gBrowser.selectedTab);
diff --git a/browser/components/preferences/tests/browser_contentblocking_standard_tcp_toggle.js b/browser/components/preferences/tests/browser_contentblocking_standard_tcp_toggle.js
index b8eed1269f534..68b863425a37a 100644
--- a/browser/components/preferences/tests/browser_contentblocking_standard_tcp_toggle.js
+++ b/browser/components/preferences/tests/browser_contentblocking_standard_tcp_toggle.js
@@ -64,7 +64,7 @@ async function waitForAndAssertPrefState(pref, expectedValue, message) {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   const defaultPrefs = Services.prefs.getDefaultBranch("");
   const previousDefaultCB = defaultPrefs.getIntPref(COOKIE_BEHAVIOR_PREF);
 
diff --git a/browser/components/preferences/tests/browser_engines.js b/browser/components/preferences/tests/browser_engines.js
index 8bc2850c06b5d..ca6e8c6425714 100644
--- a/browser/components/preferences/tests/browser_engines.js
+++ b/browser/components/preferences/tests/browser_engines.js
@@ -8,7 +8,7 @@ function getCellText(tree, i, cellName) {
   return tree.view.getCellText(i, tree.columns.getNamedColumn(cellName));
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SearchTestUtils.installSearchExtension({
     keyword: ["testing", "customkeyword"],
     search_url: "https://example.com/engine1",
diff --git a/browser/components/preferences/tests/browser_filetype_dialog.js b/browser/components/preferences/tests/browser_filetype_dialog.js
index 5839cbaee9f2c..343e32f15dcc4 100644
--- a/browser/components/preferences/tests/browser_filetype_dialog.js
+++ b/browser/components/preferences/tests/browser_filetype_dialog.js
@@ -77,7 +77,7 @@ function scrubMailtoHandlers(handlerInfo) {
 
 ("use strict");
 
-add_task(async function setup() {
+add_setup(async function() {
   // Create our dummy handlers
   let handler1 = Cc["@mozilla.org/uriloader/web-handler-app;1"].createInstance(
     Ci.nsIWebHandlerApp
diff --git a/browser/components/preferences/tests/browser_homepages_use_bookmark.js b/browser/components/preferences/tests/browser_homepages_use_bookmark.js
index 7f839c6de6a68..a84376e84426c 100644
--- a/browser/components/preferences/tests/browser_homepages_use_bookmark.js
+++ b/browser/components/preferences/tests/browser_homepages_use_bookmark.js
@@ -6,7 +6,7 @@
 const TEST_URL1 = "http://example.com/1";
 const TEST_URL2 = "http://example.com/2";
 
-add_task(async function setup() {
+add_setup(async function() {
   let oldHomepagePref = Services.prefs.getCharPref("browser.startup.homepage");
 
   await openPreferencesViaOpenPreferencesAPI("paneHome", { leaveOpen: true });
diff --git a/browser/components/preferences/tests/browser_permissions_dialog_default_perm.js b/browser/components/preferences/tests/browser_permissions_dialog_default_perm.js
index 4c44a1c2b9d51..5c5bd87d52df4 100644
--- a/browser/components/preferences/tests/browser_permissions_dialog_default_perm.js
+++ b/browser/components/preferences/tests/browser_permissions_dialog_default_perm.js
@@ -69,7 +69,7 @@ async function openPermissionsDialog() {
   await sitePermissionsDialog.document.mozSubdialogReady;
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await addDefaultTestPermissions();
 });
 
diff --git a/browser/components/preferences/tests/browser_sanitizeOnShutdown_prefLocked.js b/browser/components/preferences/tests/browser_sanitizeOnShutdown_prefLocked.js
index d927423c24513..9811ed62d1c6d 100644
--- a/browser/components/preferences/tests/browser_sanitizeOnShutdown_prefLocked.js
+++ b/browser/components/preferences/tests/browser_sanitizeOnShutdown_prefLocked.js
@@ -24,7 +24,7 @@ function testPrefStateMatchesLockedState() {
   gBrowser.removeCurrentTab();
 }
 
-add_task(function setup() {
+add_setup(function() {
   registerCleanupFunction(function resetPreferences() {
     Services.prefs.unlockPref("privacy.sanitize.sanitizeOnShutdown");
     Services.prefs.clearUserPref("privacy.history.custom");
diff --git a/browser/components/preferences/tests/browser_searchDefaultEngine.js b/browser/components/preferences/tests/browser_searchDefaultEngine.js
index 2005f339cd389..cee6fe5f6cde2 100644
--- a/browser/components/preferences/tests/browser_searchDefaultEngine.js
+++ b/browser/components/preferences/tests/browser_searchDefaultEngine.js
@@ -7,7 +7,7 @@ const { SearchTestUtils } = ChromeUtils.import(
 
 SearchTestUtils.init(this);
 
-add_task(async function setup() {
+add_setup(async function() {
   await SearchTestUtils.installSearchExtension({
     name: "engine1",
     search_url: "https://example.com/engine1",
diff --git a/browser/components/preferences/tests/browser_searchsuggestions.js b/browser/components/preferences/tests/browser_searchsuggestions.js
index d304b630c2562..918ee41cb5955 100644
--- a/browser/components/preferences/tests/browser_searchsuggestions.js
+++ b/browser/components/preferences/tests/browser_searchsuggestions.js
@@ -5,7 +5,7 @@ const PRIVATE_PREF_NAME = "browser.search.suggest.enabled.private";
 let initialUrlbarSuggestValue;
 let initialSuggestionsInPrivateValue;
 
-add_task(async function setup() {
+add_setup(async function() {
   const originalSuggest = Services.prefs.getBoolPref(SUGGEST_PREF_NAME);
   initialUrlbarSuggestValue = Services.prefs.getBoolPref(
     URLBAR_SUGGEST_PREF_NAME
diff --git a/browser/components/preferences/tests/browser_security-1.js b/browser/components/preferences/tests/browser_security-1.js
index 31cd91b69dd9e..246e45704e98e 100644
--- a/browser/components/preferences/tests/browser_security-1.js
+++ b/browser/components/preferences/tests/browser_security-1.js
@@ -24,7 +24,7 @@ registerCleanupFunction(function() {
 // each time that it wants to test various preference combinations. We
 // only use one tab (instead of opening/closing for each test) for all
 // to help improve test times on debug builds.
-add_task(async function setup() {
+add_setup(async function() {
   await openPreferencesViaOpenPreferencesAPI("privacy", { leaveOpen: true });
   registerCleanupFunction(async function() {
     BrowserTestUtils.removeTab(gBrowser.selectedTab);
diff --git a/browser/components/preferences/tests/browser_security-2.js b/browser/components/preferences/tests/browser_security-2.js
index f7748df68203a..07e571cd2e62d 100644
--- a/browser/components/preferences/tests/browser_security-2.js
+++ b/browser/components/preferences/tests/browser_security-2.js
@@ -24,7 +24,7 @@ registerCleanupFunction(function() {
 // each time that it wants to test various preference combinations. We
 // only use one tab (instead of opening/closing for each test) for all
 // to help improve test times on debug builds.
-add_task(async function setup() {
+add_setup(async function() {
   await openPreferencesViaOpenPreferencesAPI("privacy", { leaveOpen: true });
   registerCleanupFunction(async function() {
     BrowserTestUtils.removeTab(gBrowser.selectedTab);
diff --git a/browser/components/preferences/tests/browser_sync_pairing.js b/browser/components/preferences/tests/browser_sync_pairing.js
index 40b829c5572e8..16b8141403641 100644
--- a/browser/components/preferences/tests/browser_sync_pairing.js
+++ b/browser/components/preferences/tests/browser_sync_pairing.js
@@ -13,7 +13,7 @@ const { sinon } = ChromeUtils.import("resource://testing-common/Sinon.jsm");
 
 let flowCounter = 0;
 
-add_task(async function setup() {
+add_setup(async function() {
   Services.prefs.setBoolPref("identity.fxaccounts.pairing.enabled", true);
   // Sync start-up might interfere with our tests, don't let UIState send UI updates.
   const origNotifyStateUpdated = UIState._internal.notifyStateUpdated;
diff --git a/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_about.js b/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_about.js
index 591d4d3ab291b..e2822bdd71577 100644
--- a/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_about.js
+++ b/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_about.js
@@ -37,7 +37,7 @@ async function testLinkOpensUrl({ win, tab, elementId, expectedUrl }) {
 let expectedEngineAlias;
 let expectedIconURL;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.search.separatePrivateDefault", true],
diff --git a/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_about_messaging.js b/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_about_messaging.js
index c7f89dae5a92a..da4c937b88a42 100644
--- a/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_about_messaging.js
+++ b/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_about_messaging.js
@@ -58,7 +58,7 @@ async function setupMSExperimentWithMessage(message) {
   return doExperimentCleanup;
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   let { win } = await openAboutPrivateBrowsing();
   await BrowserTestUtils.closeWindow(win);
 });
diff --git a/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_about_search_banner.js b/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_about_search_banner.js
index d36f52a730986..c97592f62389d 100644
--- a/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_about_search_banner.js
+++ b/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_about_search_banner.js
@@ -16,7 +16,7 @@ const PREF_MAX_SEARCH_BANNER_SHOW_COUNT =
   "browser.search.separatePrivateDefault.ui.banner.max";
 const MAX_SHOW_COUNT = 5;
 
-add_task(async function setup() {
+add_setup(async function() {
   SpecialPowers.pushPrefEnv({
     set: [
       [PREF_UI_ENABLED, false],
diff --git a/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_concurrent.js b/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_concurrent.js
index 976f02dc68b8c..5b8be666fca30 100644
--- a/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_concurrent.js
+++ b/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_concurrent.js
@@ -11,7 +11,7 @@
 // Step 3: load a page in the tab from step 1 that checks the value of test2 is value2 and the total count in non-private storage is 1
 // Step 4: load a page in the tab from step 2 that checks the value of test is value and the total count in private storage is 1
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["dom.ipc.processCount", 1]],
   });
diff --git a/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_rememberprompt.js b/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_rememberprompt.js
index 57c067e5a6fe2..e930922969460 100644
--- a/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_rememberprompt.js
+++ b/browser/components/privatebrowsing/test/browser/browser_privatebrowsing_rememberprompt.js
@@ -5,7 +5,7 @@
 // This test makes sure that the geolocation prompt does not show a remember
 // control inside the private browsing mode.
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["dom.vr.always_support_vr", true]],
   });
diff --git a/browser/components/protections/test/browser/browser_protections_proxy.js b/browser/components/protections/test/browser/browser_protections_proxy.js
index ff02df2946998..14af593483028 100644
--- a/browser/components/protections/test/browser/browser_protections_proxy.js
+++ b/browser/components/protections/test/browser/browser_protections_proxy.js
@@ -8,7 +8,7 @@ XPCOMUtils.defineLazyModuleGetters(this, {
   Region: "resource://gre/modules/Region.jsm",
 });
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.contentblocking.report.monitor.enabled", false],
diff --git a/browser/components/protections/test/browser/browser_protections_report_ui.js b/browser/components/protections/test/browser/browser_protections_report_ui.js
index 0abff5485ec49..34bf24b41fc53 100644
--- a/browser/components/protections/test/browser/browser_protections_report_ui.js
+++ b/browser/components/protections/test/browser/browser_protections_report_ui.js
@@ -29,7 +29,7 @@ const SQL = {
   selectAll: "SELECT * FROM events",
 };
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.contentblocking.database.enabled", true],
diff --git a/browser/components/protections/test/browser/browser_protections_telemetry.js b/browser/components/protections/test/browser/browser_protections_telemetry.js
index 0f92dd2eaf9b2..113c1d05b6ee3 100644
--- a/browser/components/protections/test/browser/browser_protections_telemetry.js
+++ b/browser/components/protections/test/browser/browser_protections_telemetry.js
@@ -43,7 +43,7 @@ const LOG = {
 
 requestLongerTimeout(2);
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.vpn_promo.enabled", true],
diff --git a/browser/components/protections/test/browser/browser_protections_vpn.js b/browser/components/protections/test/browser/browser_protections_vpn.js
index f44b29c0d7e17..23107841f4bdd 100644
--- a/browser/components/protections/test/browser/browser_protections_vpn.js
+++ b/browser/components/protections/test/browser/browser_protections_vpn.js
@@ -64,7 +64,7 @@ async function revertRegions() {
   setHomeRegion(initialHomeRegion);
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.contentblocking.report.monitor.enabled", false],
diff --git a/browser/components/resistfingerprinting/test/browser/browser_dynamical_window_rounding.js b/browser/components/resistfingerprinting/test/browser/browser_dynamical_window_rounding.js
index 3a7612d77b827..3c5dc5e745157 100644
--- a/browser/components/resistfingerprinting/test/browser/browser_dynamical_window_rounding.js
+++ b/browser/components/resistfingerprinting/test/browser/browser_dynamical_window_rounding.js
@@ -346,7 +346,7 @@ async function test_findbar(aWindow) {
   BrowserTestUtils.removeTab(tab);
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["privacy.resistFingerprinting.letterboxing", true],
diff --git a/browser/components/resistfingerprinting/test/browser/browser_roundedWindow_dialogWindow.js b/browser/components/resistfingerprinting/test/browser/browser_roundedWindow_dialogWindow.js
index 63d14aeb4532b..57f60f4153a27 100644
--- a/browser/components/resistfingerprinting/test/browser/browser_roundedWindow_dialogWindow.js
+++ b/browser/components/resistfingerprinting/test/browser/browser_roundedWindow_dialogWindow.js
@@ -33,7 +33,7 @@ async function test_dialog_window() {
   await BrowserTestUtils.closeWindow(diagWin);
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["privacy.resistFingerprinting", true]],
   });
diff --git a/browser/components/resistfingerprinting/test/browser/browser_roundedWindow_newWindow.js b/browser/components/resistfingerprinting/test/browser/browser_roundedWindow_newWindow.js
index 1a18edb1925ae..aa7290a9004d6 100644
--- a/browser/components/resistfingerprinting/test/browser/browser_roundedWindow_newWindow.js
+++ b/browser/components/resistfingerprinting/test/browser/browser_roundedWindow_newWindow.js
@@ -8,7 +8,7 @@ const CC = Components.Constructor;
 let gMaxAvailWidth;
 let gMaxAvailHeight;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["privacy.resistFingerprinting", true]],
   });
diff --git a/browser/components/resistfingerprinting/test/browser/browser_spoofing_keyboard_event.js b/browser/components/resistfingerprinting/test/browser/browser_spoofing_keyboard_event.js
index aae35f6aa7864..9703fca055edc 100644
--- a/browser/components/resistfingerprinting/test/browser/browser_spoofing_keyboard_event.js
+++ b/browser/components/resistfingerprinting/test/browser/browser_spoofing_keyboard_event.js
@@ -2147,7 +2147,7 @@ function eventConsumer(aEvent) {
   aEvent.preventDefault();
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["privacy.resistFingerprinting", true]],
   });
diff --git a/browser/components/resistfingerprinting/test/browser/browser_timezone.js b/browser/components/resistfingerprinting/test/browser/browser_timezone.js
index f7d9b5e7d0002..5baa13124e73a 100644
--- a/browser/components/resistfingerprinting/test/browser/browser_timezone.js
+++ b/browser/components/resistfingerprinting/test/browser/browser_timezone.js
@@ -3,7 +3,7 @@
  *               UTC timezone after fingerprinting resistance is enabled.
  */
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["privacy.resistFingerprinting", true]],
   });
diff --git a/browser/components/search/test/browser/browser_contentSearchUI.js b/browser/components/search/test/browser/browser_contentSearchUI.js
index c032dd89b7680..dc017791170e0 100644
--- a/browser/components/search/test/browser/browser_contentSearchUI.js
+++ b/browser/components/search/test/browser/browser_contentSearchUI.js
@@ -251,7 +251,7 @@ let extension1;
 let extension2;
 let currentEngineName;
 
-add_task(async function setup() {
+add_setup(async function() {
   let originalOnMessageSearch = ContentSearch._onMessageSearch;
   let originalOnMessageManageEngines = ContentSearch._onMessageManageEngines;
 
diff --git a/browser/components/search/test/browser/browser_contentSearchUI_default.js b/browser/components/search/test/browser/browser_contentSearchUI_default.js
index 893f090776203..19c1e84af688a 100644
--- a/browser/components/search/test/browser/browser_contentSearchUI_default.js
+++ b/browser/components/search/test/browser/browser_contentSearchUI_default.js
@@ -9,7 +9,7 @@ let extension;
 let defaultEngine;
 let addedEngine;
 
-add_task(async function setup() {
+add_setup(async function() {
   // Disable window occlusion. Bug 1733955
   if (navigator.platform.indexOf("Win") == 0) {
     await SpecialPowers.pushPrefEnv({
diff --git a/browser/components/search/test/browser/browser_contextSearchTabPosition.js b/browser/components/search/test/browser/browser_contextSearchTabPosition.js
index 889e094ba566d..5c39b5fa1bf55 100644
--- a/browser/components/search/test/browser/browser_contextSearchTabPosition.js
+++ b/browser/components/search/test/browser/browser_contextSearchTabPosition.js
@@ -4,7 +4,7 @@
 
 let engine;
 
-add_task(async function setup() {
+add_setup(async function() {
   engine = await SearchTestUtils.promiseNewSearchEngine(
     getRootDirectory(gTestPath) + "testEngine.xml"
   );
diff --git a/browser/components/search/test/browser/browser_contextmenu.js b/browser/components/search/test/browser/browser_contextmenu.js
index 346ae02230e6a..a569cff279e6f 100644
--- a/browser/components/search/test/browser/browser_contextmenu.js
+++ b/browser/components/search/test/browser/browser_contextmenu.js
@@ -26,7 +26,7 @@ let extensions = [];
 let oldDefaultEngine;
 let oldDefaultPrivateEngine;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.search.separatePrivateDefault", true],
diff --git a/browser/components/search/test/browser/browser_contextmenu_whereToOpenLink.js b/browser/components/search/test/browser/browser_contextmenu_whereToOpenLink.js
index 192a1681508ac..bd4c0fc0b460d 100644
--- a/browser/components/search/test/browser/browser_contextmenu_whereToOpenLink.js
+++ b/browser/components/search/test/browser/browser_contextmenu_whereToOpenLink.js
@@ -14,7 +14,7 @@ const ENGINE_NAME = "mozSearch";
 const ENGINE_URL =
   "https://example.com/browser/browser/components/search/test/browser/mozsearch.sjs";
 
-add_task(async function setup() {
+add_setup(async function() {
   await Services.search.init();
 
   await SearchTestUtils.installSearchExtension({
diff --git a/browser/components/search/test/browser/browser_google_behavior.js b/browser/components/search/test/browser/browser_google_behavior.js
index 726d23418d9bc..e0ce9180ac96c 100644
--- a/browser/components/search/test/browser/browser_google_behavior.js
+++ b/browser/components/search/test/browser/browser_google_behavior.js
@@ -84,7 +84,7 @@ function promiseContentSearchReady(browser) {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await Services.search.init();
 });
 
diff --git a/browser/components/search/test/browser/browser_ime_composition.js b/browser/components/search/test/browser/browser_ime_composition.js
index b25e64b8c8e51..2e16ec8a35ddc 100644
--- a/browser/components/search/test/browser/browser_ime_composition.js
+++ b/browser/components/search/test/browser/browser_ime_composition.js
@@ -3,7 +3,7 @@
 
 // Tests ime composition handling on searchbar.
 
-add_task(async function setup() {
+add_setup(async function() {
   await gCUITestUtils.addSearchBar();
 
   await SearchTestUtils.installSearchExtension();
diff --git a/browser/components/search/test/browser/browser_search_telemetry_aboutHome.js b/browser/components/search/test/browser/browser_search_telemetry_aboutHome.js
index 9356d0761780d..649510d7a7cb1 100644
--- a/browser/components/search/test/browser/browser_search_telemetry_aboutHome.js
+++ b/browser/components/search/test/browser/browser_search_telemetry_aboutHome.js
@@ -2,7 +2,7 @@
 
 const SCALAR_ABOUT_HOME = "browser.engagement.navigation.about_home";
 
-add_task(async function setup() {
+add_setup(async function() {
   // about:home uses IndexedDB. However, the test finishes too quickly and doesn't
   // allow it enougth time to save. So it throws. This disables all the uncaught
   // exception in this file and that's the reason why we split about:home tests
diff --git a/browser/components/search/test/browser/browser_search_telemetry_content.js b/browser/components/search/test/browser/browser_search_telemetry_content.js
index 35df332b25f7e..ee2c3c30b9503 100644
--- a/browser/components/search/test/browser/browser_search_telemetry_content.js
+++ b/browser/components/search/test/browser/browser_search_telemetry_content.js
@@ -4,7 +4,7 @@ const BASE_PROBE_NAME = "browser.engagement.navigation.";
 const SCALAR_CONTEXT_MENU = BASE_PROBE_NAME + "contextmenu";
 const SCALAR_ABOUT_NEWTAB = BASE_PROBE_NAME + "about_newtab";
 
-add_task(async function setup() {
+add_setup(async function() {
   // Create two new search engines. Mark one as the default engine, so
   // the test don't crash. We need to engines for this test as the searchbar
   // in content doesn't display the default search engine among the one-off engines.
diff --git a/browser/components/search/test/browser/browser_search_telemetry_searchbar.js b/browser/components/search/test/browser/browser_search_telemetry_searchbar.js
index 2023f18ca2a18..eecd0ed6f7043 100644
--- a/browser/components/search/test/browser/browser_search_telemetry_searchbar.js
+++ b/browser/components/search/test/browser/browser_search_telemetry_searchbar.js
@@ -48,7 +48,7 @@ function clickSearchbarSuggestion(entryName, clickOptions = {}) {
   EventUtils.synthesizeMouseAtCenter(richlistitem, clickOptions);
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await gCUITestUtils.addSearchBar();
   const url = getRootDirectory(gTestPath) + "telemetrySearchSuggestions.xml";
   suggestionEngine = await SearchTestUtils.promiseNewSearchEngine(url, "");
diff --git a/browser/components/search/test/browser/browser_search_telemetry_sources.js b/browser/components/search/test/browser/browser_search_telemetry_sources.js
index 8aaf6e931b834..4e7f59161bb5f 100644
--- a/browser/components/search/test/browser/browser_search_telemetry_sources.js
+++ b/browser/components/search/test/browser/browser_search_telemetry_sources.js
@@ -68,7 +68,7 @@ async function waitForIdle() {
 SearchTestUtils.init(this);
 UrlbarTestUtils.init(this);
 
-add_task(async function setup() {
+add_setup(async function() {
   SearchSERPTelemetry.overrideSearchTelemetryForTests(TEST_PROVIDER_INFO);
   await waitForIdle();
   await SpecialPowers.pushPrefEnv({
diff --git a/browser/components/search/test/browser/browser_search_telemetry_sources_ads.js b/browser/components/search/test/browser/browser_search_telemetry_sources_ads.js
index db8c0bc85bb8e..6aa9505e4672c 100644
--- a/browser/components/search/test/browser/browser_search_telemetry_sources_ads.js
+++ b/browser/components/search/test/browser/browser_search_telemetry_sources_ads.js
@@ -49,7 +49,7 @@ async function waitForIdle() {
   }
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   SearchSERPTelemetry.overrideSearchTelemetryForTests(TEST_PROVIDER_INFO);
   await waitForIdle();
   // Enable local telemetry recording for the duration of the tests.
diff --git a/browser/components/search/test/browser/browser_search_telemetry_sources_navigation.js b/browser/components/search/test/browser/browser_search_telemetry_sources_navigation.js
index 531f328c797f8..f7b886020d766 100644
--- a/browser/components/search/test/browser/browser_search_telemetry_sources_navigation.js
+++ b/browser/components/search/test/browser/browser_search_telemetry_sources_navigation.js
@@ -70,7 +70,7 @@ UrlbarTestUtils.init(this);
 
 let tab;
 
-add_task(async function setup() {
+add_setup(async function() {
   searchCounts.clear();
   Services.telemetry.clearScalars();
 
diff --git a/browser/components/search/test/browser/browser_searchbar_addEngine.js b/browser/components/search/test/browser/browser_searchbar_addEngine.js
index 0aef75ec2b557..d2e61e5093b53 100644
--- a/browser/components/search/test/browser/browser_searchbar_addEngine.js
+++ b/browser/components/search/test/browser/browser_searchbar_addEngine.js
@@ -14,7 +14,7 @@ const { PromptTestUtils } = ChromeUtils.import(
 const searchPopup = document.getElementById("PopupSearchAutoComplete");
 let searchbar;
 
-add_task(async function setup() {
+add_setup(async function() {
   searchbar = await gCUITestUtils.addSearchBar();
 
   registerCleanupFunction(async function() {
diff --git a/browser/components/search/test/browser/browser_searchbar_context.js b/browser/components/search/test/browser/browser_searchbar_context.js
index 481e3dfa4f524..8f4387ca950e3 100644
--- a/browser/components/search/test/browser/browser_searchbar_context.js
+++ b/browser/components/search/test/browser/browser_searchbar_context.js
@@ -9,7 +9,7 @@
 
 let win;
 
-add_task(async function setup() {
+add_setup(async function() {
   await gCUITestUtils.addSearchBar();
 
   win = await BrowserTestUtils.openNewBrowserWindow();
diff --git a/browser/components/search/test/browser/browser_searchbar_default.js b/browser/components/search/test/browser/browser_searchbar_default.js
index 1b5c6fa17b1e5..1433025b67d77 100644
--- a/browser/components/search/test/browser/browser_searchbar_default.js
+++ b/browser/components/search/test/browser/browser_searchbar_default.js
@@ -16,7 +16,7 @@ const templatePrivate = "https://example.com/?query=";
 
 const searchPopup = document.getElementById("PopupSearchAutoComplete");
 
-add_task(async function setup() {
+add_setup(async function() {
   await gCUITestUtils.addSearchBar();
 
   await SpecialPowers.pushPrefEnv({
diff --git a/browser/components/search/test/browser/browser_searchbar_enter.js b/browser/components/search/test/browser/browser_searchbar_enter.js
index 04e94ceafce82..c6a3cbcc74b06 100644
--- a/browser/components/search/test/browser/browser_searchbar_enter.js
+++ b/browser/components/search/test/browser/browser_searchbar_enter.js
@@ -5,7 +5,7 @@
 
 // Test the behavior for enter key.
 
-add_task(async function setup() {
+add_setup(async function() {
   await gCUITestUtils.addSearchBar();
 
   await SearchTestUtils.installSearchExtension();
diff --git a/browser/components/search/test/browser/browser_searchbar_keyboard_navigation.js b/browser/components/search/test/browser/browser_searchbar_keyboard_navigation.js
index 504dd3aef5d48..95b32fc4fb0d2 100644
--- a/browser/components/search/test/browser/browser_searchbar_keyboard_navigation.js
+++ b/browser/components/search/test/browser/browser_searchbar_keyboard_navigation.js
@@ -47,7 +47,7 @@ async function checkHeader(engine) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   searchbar = await gCUITestUtils.addSearchBar();
   textbox = searchbar.textbox;
 
diff --git a/browser/components/search/test/browser/browser_searchbar_openpopup.js b/browser/components/search/test/browser/browser_searchbar_openpopup.js
index 1d8c49a5bb7e6..2d0177b03b751 100644
--- a/browser/components/search/test/browser/browser_searchbar_openpopup.js
+++ b/browser/components/search/test/browser/browser_searchbar_openpopup.js
@@ -34,7 +34,7 @@ let searchIcon;
 let goButton;
 let engine;
 
-add_task(async function setup() {
+add_setup(async function() {
   searchbar = await gCUITestUtils.addSearchBar();
   textbox = searchbar.textbox;
   searchIcon = searchbar.querySelector(".searchbar-search-button");
diff --git a/browser/components/search/test/browser/browser_searchbar_results.js b/browser/components/search/test/browser/browser_searchbar_results.js
index 1744ce0dacaf7..283a333f71e8e 100644
--- a/browser/components/search/test/browser/browser_searchbar_results.js
+++ b/browser/components/search/test/browser/browser_searchbar_results.js
@@ -1,7 +1,7 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
-add_task(async function setup() {
+add_setup(async function() {
   await gCUITestUtils.addSearchBar();
   await clearSearchbarHistory();
   let defaultEngine = await Services.search.getDefault();
diff --git a/browser/components/search/test/browser/browser_searchbar_smallpanel_keyboard_navigation.js b/browser/components/search/test/browser/browser_searchbar_smallpanel_keyboard_navigation.js
index 86c50dfd4de76..fe199e1a2e4da 100644
--- a/browser/components/search/test/browser/browser_searchbar_smallpanel_keyboard_navigation.js
+++ b/browser/components/search/test/browser/browser_searchbar_smallpanel_keyboard_navigation.js
@@ -23,7 +23,7 @@ let searchbar;
 let textbox;
 let searchIcon;
 
-add_task(async function setup() {
+add_setup(async function() {
   searchbar = await gCUITestUtils.addSearchBar();
   registerCleanupFunction(() => {
     gCUITestUtils.removeSearchBar();
diff --git a/browser/components/sessionstore/test/browser_350525.js b/browser/components/sessionstore/test/browser_350525.js
index b046b1c65c627..812e5f1310313 100644
--- a/browser/components/sessionstore/test/browser_350525.js
+++ b/browser/components/sessionstore/test/browser_350525.js
@@ -1,6 +1,6 @@
 "use strict";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["dom.ipc.processCount", 1]],
   });
diff --git a/browser/components/sessionstore/test/browser_354894_perwindowpb.js b/browser/components/sessionstore/test/browser_354894_perwindowpb.js
index d0e3aa99e0871..43114f69dd658 100644
--- a/browser/components/sessionstore/test/browser_354894_perwindowpb.js
+++ b/browser/components/sessionstore/test/browser_354894_perwindowpb.js
@@ -75,7 +75,7 @@ function getBrowserWindowsCount() {
   return { open, winstates };
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // Make sure we've only got one browser window to start with
   let { open, winstates } = getBrowserWindowsCount();
   is(open, 1, "Should only be one open window");
diff --git a/browser/components/sessionstore/test/browser_393716.js b/browser/components/sessionstore/test/browser_393716.js
index ff94dc7481db7..6a98435724535 100644
--- a/browser/components/sessionstore/test/browser_393716.js
+++ b/browser/components/sessionstore/test/browser_393716.js
@@ -5,7 +5,7 @@
 
 const URL = "about:config";
 
-add_task(async function setup() {
+add_setup(async function() {
   // Make sure that the field of which we restore the state is visible on load.
   await SpecialPowers.pushPrefEnv({
     set: [["browser.aboutConfig.showWarning", false]],
diff --git a/browser/components/sessionstore/test/browser_625016.js b/browser/components/sessionstore/test/browser_625016.js
index c6da28d2e9843..e5f32d40df0a9 100644
--- a/browser/components/sessionstore/test/browser_625016.js
+++ b/browser/components/sessionstore/test/browser_625016.js
@@ -1,7 +1,7 @@
 /* Any copyright is dedicated to the Public Domain.
    http://creativecommons.org/publicdomain/zero/1.0/ */
 
-add_task(async function setup() {
+add_setup(async function() {
   /** Test for Bug 625016 - Restore windows closed in succession to quit (non-OSX only) **/
 
   // We'll test this by opening a new window, waiting for the save
diff --git a/browser/components/sessionstore/test/browser_background_tab_crash.js b/browser/components/sessionstore/test/browser_background_tab_crash.js
index c74fdc5eba10b..a500d489b192c 100644
--- a/browser/components/sessionstore/test/browser_background_tab_crash.js
+++ b/browser/components/sessionstore/test/browser_background_tab_crash.js
@@ -111,7 +111,7 @@ async function crashBackgroundTabs(tabs) {
   }
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // We'll simplify by making sure we only ever one content process for this
   // test.
   await SpecialPowers.pushPrefEnv({
diff --git a/browser/components/sessionstore/test/browser_formdata_xpath.js b/browser/components/sessionstore/test/browser_formdata_xpath.js
index 99087a56009de..37644d7c5bff8 100644
--- a/browser/components/sessionstore/test/browser_formdata_xpath.js
+++ b/browser/components/sessionstore/test/browser_formdata_xpath.js
@@ -8,7 +8,7 @@ const URL = ROOT + "browser_formdata_xpath_sample.html";
 /**
  * Bug 346337 - Generic form data restoration tests.
  */
-add_task(function setup() {
+add_setup(function() {
   // make sure we don't save form data at all (except for tab duplication)
   Services.prefs.setIntPref("browser.sessionstore.privacy_level", 2);
 
diff --git a/browser/components/sessionstore/test/browser_pinned_tabs.js b/browser/components/sessionstore/test/browser_pinned_tabs.js
index 2f03e04d4cead..a4d1cce85bd60 100644
--- a/browser/components/sessionstore/test/browser_pinned_tabs.js
+++ b/browser/components/sessionstore/test/browser_pinned_tabs.js
@@ -33,7 +33,7 @@ function promiseSessionStoreLoads(numberOfLoads) {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.sessionstore.restore_on_demand", true],
diff --git a/browser/components/sessionstore/test/browser_restore_container_tabs_oa.js b/browser/components/sessionstore/test/browser_restore_container_tabs_oa.js
index 6bfe5c53670e8..fc22ab917fd2e 100644
--- a/browser/components/sessionstore/test/browser_restore_container_tabs_oa.js
+++ b/browser/components/sessionstore/test/browser_restore_container_tabs_oa.js
@@ -34,7 +34,7 @@ function handleEventLocal(aEvent) {
 
 var NUM_DIFF_TAB_MODES = NUM_USER_CONTEXTS + 1; /** regular tab */
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       // Set the pref to true so we know exactly how many tabs should be restoring at
diff --git a/browser/components/sessionstore/test/browser_restore_private_tab_os.js b/browser/components/sessionstore/test/browser_restore_private_tab_os.js
index 655ffe48e8e35..feecfe327a84a 100644
--- a/browser/components/sessionstore/test/browser_restore_private_tab_os.js
+++ b/browser/components/sessionstore/test/browser_restore_private_tab_os.js
@@ -8,7 +8,7 @@ const TEST_URI =
   "https://example.com/" +
   "browser/browser/components/sessionstore/test/empty.html";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       // Set the pref to true so we know exactly how many tabs should be restoring at
diff --git a/browser/components/sessionstore/test/browser_restore_reversed_z_order.js b/browser/components/sessionstore/test/browser_restore_reversed_z_order.js
index 6cb4964c13dae..298f8ccaab79d 100644
--- a/browser/components/sessionstore/test/browser_restore_reversed_z_order.js
+++ b/browser/components/sessionstore/test/browser_restore_reversed_z_order.js
@@ -10,7 +10,7 @@ let gTestURLsMap = new Map([
 ]);
 let gBrowserState;
 
-add_task(async function setup() {
+add_setup(async function() {
   let windows = [];
   let count = 0;
   for (let url of gTestURLsMap.keys()) {
diff --git a/browser/components/sessionstore/test/browser_revive_crashed_bg_tabs.js b/browser/components/sessionstore/test/browser_revive_crashed_bg_tabs.js
index 036ec27bfcfda..08225fa6d67e5 100644
--- a/browser/components/sessionstore/test/browser_revive_crashed_bg_tabs.js
+++ b/browser/components/sessionstore/test/browser_revive_crashed_bg_tabs.js
@@ -14,7 +14,7 @@ const PAGE_1 =
 const PAGE_2 =
   "data:text/html,<html><body>Another%20regular,%20everyday,%20normal%20page.";
 
-add_task(async function setup() {
+add_setup(async function() {
   await pushPrefs(
     ["dom.ipc.processCount", 1],
     ["browser.sessionstore.restore_on_demand", false]
diff --git a/browser/components/sessionstore/test/browser_tabs_in_urlbar.js b/browser/components/sessionstore/test/browser_tabs_in_urlbar.js
index 2582a25ae2272..08fdaebb8495d 100644
--- a/browser/components/sessionstore/test/browser_tabs_in_urlbar.js
+++ b/browser/components/sessionstore/test/browser_tabs_in_urlbar.js
@@ -27,7 +27,7 @@ const { UrlbarTestUtils } = ChromeUtils.import(
 
 var stateBackup = ss.getBrowserState();
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       // Set the pref to true so we know exactly how many tabs should be restoring at
diff --git a/browser/components/sessionstore/test/browser_windowStateContainer.js b/browser/components/sessionstore/test/browser_windowStateContainer.js
index bf255b99c43de..d416fb8e3d06d 100644
--- a/browser/components/sessionstore/test/browser_windowStateContainer.js
+++ b/browser/components/sessionstore/test/browser_windowStateContainer.js
@@ -2,7 +2,7 @@
 
 requestLongerTimeout(2);
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["dom.ipc.processCount", 1]],
   });
diff --git a/browser/components/sessionstore/test/unit/test_final_write_cleanup.js b/browser/components/sessionstore/test/unit/test_final_write_cleanup.js
index 951a91bb174d6..3660c156c2604 100644
--- a/browser/components/sessionstore/test/unit/test_final_write_cleanup.js
+++ b/browser/components/sessionstore/test/unit/test_final_write_cleanup.js
@@ -31,7 +31,7 @@ async function prepareWithLimit(back, fwd) {
   await SessionWriter.wipe();
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   registerCleanupFunction(() => SessionWriter.wipe());
 });
 
diff --git a/browser/components/shell/test/unit/test_macOS_showSecurityPreferences.js b/browser/components/shell/test/unit/test_macOS_showSecurityPreferences.js
index 69e09db70aaaf..8550f0331a0a0 100644
--- a/browser/components/shell/test/unit/test_macOS_showSecurityPreferences.js
+++ b/browser/components/shell/test/unit/test_macOS_showSecurityPreferences.js
@@ -15,7 +15,7 @@ function killSystemPreferences() {
   return process.exitValue;
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   info("Ensure System Preferences isn't already running");
   killSystemPreferences();
 });
diff --git a/browser/components/tests/browser/browser_initial_tab_remoteType.js b/browser/components/tests/browser/browser_initial_tab_remoteType.js
index 93f5eb682ad71..de486bfeb0dfc 100644
--- a/browser/components/tests/browser/browser_initial_tab_remoteType.js
+++ b/browser/components/tests/browser/browser_initial_tab_remoteType.js
@@ -99,7 +99,7 @@ function constructOnePageCmdLine(aURL) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   NewTabPagePreloading.removePreloadedBrowser(window);
 
   await SpecialPowers.pushPrefEnv({
diff --git a/browser/components/translation/test/browser_translation_bing.js b/browser/components/translation/test/browser_translation_bing.js
index 741fbd248daf4..8462833888565 100644
--- a/browser/components/translation/test/browser_translation_bing.js
+++ b/browser/components/translation/test/browser_translation_bing.js
@@ -16,7 +16,7 @@ const { TranslationDocument } = ChromeUtils.import(
   "resource:///modules/translation/TranslationDocument.jsm"
 );
 
-add_task(async function setup() {
+add_setup(async function() {
   Services.prefs.setCharPref(kClientIdPref, "testClient");
   Services.prefs.setCharPref(kClientSecretPref, "testSecret");
 
diff --git a/browser/components/translation/test/browser_translation_telemetry.js b/browser/components/translation/test/browser_translation_telemetry.js
index 3af9cd993fc99..768daea7c18be 100644
--- a/browser/components/translation/test/browser_translation_telemetry.js
+++ b/browser/components/translation/test/browser_translation_telemetry.js
@@ -167,7 +167,7 @@ function simulateUserSelectInMenulist(menulist, value) {
   menulist.doCommand();
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   const setupPrefs = prefs => {
     let prefsBackup = {};
     for (let p of prefs) {
diff --git a/browser/components/translation/test/browser_translation_yandex.js b/browser/components/translation/test/browser_translation_yandex.js
index fa9559556acb1..723cc5946b2e3 100644
--- a/browser/components/translation/test/browser_translation_yandex.js
+++ b/browser/components/translation/test/browser_translation_yandex.js
@@ -25,7 +25,7 @@ const { Translation } = ChromeUtils.import(
   "resource:///modules/translation/TranslationParent.jsm"
 );
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       [kEnginePref, "Yandex"],
diff --git a/browser/components/uitour/test/browser_UITour_showProtectionReport.js b/browser/components/uitour/test/browser_UITour_showProtectionReport.js
index 2c23362b4cfac..78ac10dc2d517 100644
--- a/browser/components/uitour/test/browser_UITour_showProtectionReport.js
+++ b/browser/components/uitour/test/browser_UITour_showProtectionReport.js
@@ -8,7 +8,7 @@ var gContentAPI;
 
 add_task(setup_UITourTest);
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.contentblocking.database.enabled", false],
diff --git a/browser/components/uitour/test/browser_UITour_sync.js b/browser/components/uitour/test/browser_UITour_sync.js
index 9859853ef1571..59abcb0d791c0 100644
--- a/browser/components/uitour/test/browser_UITour_sync.js
+++ b/browser/components/uitour/test/browser_UITour_sync.js
@@ -15,7 +15,7 @@ registerCleanupFunction(function() {
 
 add_task(setup_UITourTest);
 
-add_task(async function setup() {
+add_setup(async function() {
   Services.prefs.setCharPref(
     "identity.fxaccounts.remote.root",
     "https://example.com"
diff --git a/browser/components/urlbar/tests/browser/browser_action_searchengine.js b/browser/components/urlbar/tests/browser/browser_action_searchengine.js
index 18d77cef15b42..70c65fa4abeef 100644
--- a/browser/components/urlbar/tests/browser/browser_action_searchengine.js
+++ b/browser/components/urlbar/tests/browser/browser_action_searchengine.js
@@ -6,7 +6,7 @@
  * expected URL for the engine.
  */
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.search.separatePrivateDefault.ui.enabled", true],
diff --git a/browser/components/urlbar/tests/browser/browser_autoFill_trimURLs.js b/browser/components/urlbar/tests/browser/browser_autoFill_trimURLs.js
index 1d4b8056819bc..b33ca5c4555d7 100644
--- a/browser/components/urlbar/tests/browser/browser_autoFill_trimURLs.js
+++ b/browser/components/urlbar/tests/browser/browser_autoFill_trimURLs.js
@@ -6,7 +6,7 @@
 
 "use strict";
 
-add_task(async function setup() {
+add_setup(async function() {
   const PREF_TRIMURL = "browser.urlbar.trimURLs";
   const PREF_AUTOFILL = "browser.urlbar.autoFill";
 
diff --git a/browser/components/urlbar/tests/browser/browser_autocomplete_enter_race.js b/browser/components/urlbar/tests/browser/browser_autocomplete_enter_race.js
index 10318620ddb2b..2c725d2cffb4d 100644
--- a/browser/components/urlbar/tests/browser/browser_autocomplete_enter_race.js
+++ b/browser/components/urlbar/tests/browser/browser_autocomplete_enter_race.js
@@ -9,7 +9,7 @@
 
 // The order of these tests matters!
 
-add_task(async function setup() {
+add_setup(async function() {
   let bm = await PlacesUtils.bookmarks.insert({
     parentGuid: PlacesUtils.bookmarks.unfiledGuid,
     url: "http://example.com/?q=%s",
diff --git a/browser/components/urlbar/tests/browser/browser_edit_invalid_url.js b/browser/components/urlbar/tests/browser/browser_edit_invalid_url.js
index a74196a129eb5..31ac70672d7b7 100644
--- a/browser/components/urlbar/tests/browser/browser_edit_invalid_url.js
+++ b/browser/components/urlbar/tests/browser/browser_edit_invalid_url.js
@@ -7,7 +7,7 @@
 
 const url = BrowserUIUtils.trimURLProtocol + "invalid.somehost/mytest";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["browser.urlbar.trimURLs", true]],
   });
diff --git a/browser/components/urlbar/tests/browser/browser_enter.js b/browser/components/urlbar/tests/browser/browser_enter.js
index 439496bd9bde9..252e4ee5eade0 100644
--- a/browser/components/urlbar/tests/browser/browser_enter.js
+++ b/browser/components/urlbar/tests/browser/browser_enter.js
@@ -6,7 +6,7 @@
 const TEST_VALUE = "example.com/\xF7?\xF7";
 const START_VALUE = "example.com/%C3%B7?%C3%B7";
 
-add_task(async function setup() {
+add_setup(async function() {
   const engine = await SearchTestUtils.promiseNewSearchEngine(
     getRootDirectory(gTestPath) + "searchSuggestionEngine.xml"
   );
diff --git a/browser/components/urlbar/tests/browser/browser_inputHistory.js b/browser/components/urlbar/tests/browser/browser_inputHistory.js
index 3974da3d2c80b..e6af195b36bc3 100644
--- a/browser/components/urlbar/tests/browser/browser_inputHistory.js
+++ b/browser/components/urlbar/tests/browser/browser_inputHistory.js
@@ -53,7 +53,7 @@ async function decayInputHistory() {
   await PlacesTestUtils.promiseAsyncUpdates();
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // Use new window to avoid timeout failure for autocomplete popup happens on Linux TV.
   win = await BrowserTestUtils.openNewBrowserWindow();
 
diff --git a/browser/components/urlbar/tests/browser/browser_inputHistory_emptystring.js b/browser/components/urlbar/tests/browser/browser_inputHistory_emptystring.js
index 8fc44329ff78d..607de4065223c 100644
--- a/browser/components/urlbar/tests/browser/browser_inputHistory_emptystring.js
+++ b/browser/components/urlbar/tests/browser/browser_inputHistory_emptystring.js
@@ -56,7 +56,7 @@ async function do_test(openFn, pickMethod) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await PlacesUtils.history.clear();
   for (let i = 0; i < 5; i++) {
     await PlacesTestUtils.addVisits(TEST_URL);
diff --git a/browser/components/urlbar/tests/browser/browser_keyword.js b/browser/components/urlbar/tests/browser/browser_keyword.js
index 8b6d84ec396fe..f8f2d66f71166 100644
--- a/browser/components/urlbar/tests/browser/browser_keyword.js
+++ b/browser/components/urlbar/tests/browser/browser_keyword.js
@@ -32,7 +32,7 @@ function assertURL(result, expectedUrl, keyword, input, postData) {
 
 const TEST_URL = `${TEST_BASE_URL}print_postdata.sjs`;
 
-add_task(async function setup() {
+add_setup(async function() {
   await PlacesUtils.keywords.insert({
     keyword: "get",
     url: TEST_URL + "?q=%s",
diff --git a/browser/components/urlbar/tests/browser/browser_keywordBookmarklets.js b/browser/components/urlbar/tests/browser/browser_keywordBookmarklets.js
index 97220fc2682d6..1f9465a08fcb5 100644
--- a/browser/components/urlbar/tests/browser/browser_keywordBookmarklets.js
+++ b/browser/components/urlbar/tests/browser/browser_keywordBookmarklets.js
@@ -3,7 +3,7 @@
 
 "use strict";
 
-add_task(async function setup() {
+add_setup(async function() {
   let bm = await PlacesUtils.bookmarks.insert({
     parentGuid: PlacesUtils.bookmarks.unfiledGuid,
     title: "bookmarklet",
diff --git a/browser/components/urlbar/tests/browser/browser_keywordSearch.js b/browser/components/urlbar/tests/browser/browser_keywordSearch.js
index 5ba5805589cf1..47eafeed4b2f6 100644
--- a/browser/components/urlbar/tests/browser/browser_keywordSearch.js
+++ b/browser/components/urlbar/tests/browser/browser_keywordSearch.js
@@ -16,7 +16,7 @@ var gTests = [
   },
 ];
 
-add_task(async function setup() {
+add_setup(async function() {
   let engine = await SearchTestUtils.promiseNewSearchEngine(
     getRootDirectory(gTestPath) + "searchSuggestionEngine.xml"
   );
diff --git a/browser/components/urlbar/tests/browser/browser_keywordSearch_postData.js b/browser/components/urlbar/tests/browser/browser_keywordSearch_postData.js
index 8484cd778dfdb..d7bce19165b02 100644
--- a/browser/components/urlbar/tests/browser/browser_keywordSearch_postData.js
+++ b/browser/components/urlbar/tests/browser/browser_keywordSearch_postData.js
@@ -21,7 +21,7 @@ var gTests = [
   },
 ];
 
-add_task(async function setup() {
+add_setup(async function() {
   let engine = await SearchTestUtils.promiseNewSearchEngine(
     getRootDirectory(gTestPath) + "POSTSearchEngine.xml"
   );
diff --git a/browser/components/urlbar/tests/browser/browser_loadRace.js b/browser/components/urlbar/tests/browser/browser_loadRace.js
index 4e1e48e5d6578..db9b46905c5bf 100644
--- a/browser/components/urlbar/tests/browser/browser_loadRace.js
+++ b/browser/components/urlbar/tests/browser/browser_loadRace.js
@@ -7,7 +7,7 @@
 // a page load whilst we're getting the search url, then we don't handle the
 // original search query.
 
-add_task(async function setup() {
+add_setup(async function() {
   sandbox = sinon.createSandbox();
 
   registerCleanupFunction(async () => {
diff --git a/browser/components/urlbar/tests/browser/browser_locationBarCommand.js b/browser/components/urlbar/tests/browser/browser_locationBarCommand.js
index aeffac30456ab..a611a3d15b8ab 100644
--- a/browser/components/urlbar/tests/browser/browser_locationBarCommand.js
+++ b/browser/components/urlbar/tests/browser/browser_locationBarCommand.js
@@ -9,7 +9,7 @@
 const TEST_VALUE = "example.com";
 const START_VALUE = "example.org";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.altClickSave", true],
diff --git a/browser/components/urlbar/tests/browser/browser_paste_multi_lines.js b/browser/components/urlbar/tests/browser/browser_paste_multi_lines.js
index 046e27b78ed3f..c50504c29a456 100644
--- a/browser/components/urlbar/tests/browser/browser_paste_multi_lines.js
+++ b/browser/components/urlbar/tests/browser/browser_paste_multi_lines.js
@@ -120,7 +120,7 @@ const TEST_DATA = [
   },
 ];
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       // There are cases that URLBar loses focus before assertion of this test.
diff --git a/browser/components/urlbar/tests/browser/browser_placeholder.js b/browser/components/urlbar/tests/browser/browser_placeholder.js
index 95b85bb7640c4..7c0b9883e7351 100644
--- a/browser/components/urlbar/tests/browser/browser_placeholder.js
+++ b/browser/components/urlbar/tests/browser/browser_placeholder.js
@@ -13,7 +13,7 @@ var tabs = [];
 
 var noEngineString;
 
-add_task(async function setup() {
+add_setup(async function() {
   originalEngine = await Services.search.getDefault();
   [noEngineString, expectedString] = (
     await document.l10n.formatMessages([
diff --git a/browser/components/urlbar/tests/browser/browser_remotetab.js b/browser/components/urlbar/tests/browser/browser_remotetab.js
index e985e274e1f26..c76a2508466e5 100644
--- a/browser/components/urlbar/tests/browser/browser_remotetab.js
+++ b/browser/components/urlbar/tests/browser/browser_remotetab.js
@@ -32,7 +32,7 @@ const REMOTE_TAB = {
   ],
 };
 
-add_task(async function setup() {
+add_setup(async function() {
   sandbox = sinon.createSandbox();
 
   let originalSyncedTabsInternal = SyncedTabs._internal;
diff --git a/browser/components/urlbar/tests/browser/browser_remove_match.js b/browser/components/urlbar/tests/browser/browser_remove_match.js
index b377c0a230679..69fde8aba66fc 100644
--- a/browser/components/urlbar/tests/browser/browser_remove_match.js
+++ b/browser/components/urlbar/tests/browser/browser_remove_match.js
@@ -5,7 +5,7 @@ XPCOMUtils.defineLazyModuleGetters(this, {
   FormHistory: "resource://gre/modules/FormHistory.jsm",
 });
 
-add_task(async function setup() {
+add_setup(async function() {
   await SearchTestUtils.installSearchExtension();
 
   let engine = Services.search.getEngineByName("Example");
diff --git a/browser/components/urlbar/tests/browser/browser_retainedResultsOnFocus.js b/browser/components/urlbar/tests/browser/browser_retainedResultsOnFocus.js
index c990e30a6c4e4..a82b24810efde 100644
--- a/browser/components/urlbar/tests/browser/browser_retainedResultsOnFocus.js
+++ b/browser/components/urlbar/tests/browser/browser_retainedResultsOnFocus.js
@@ -69,7 +69,7 @@ async function checkDoesNotOpenOnFocus(win) {
   await promiseState;
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["browser.urlbar.autoFill", true]],
   });
diff --git a/browser/components/urlbar/tests/browser/browser_searchHistoryLimit.js b/browser/components/urlbar/tests/browser/browser_searchHistoryLimit.js
index 02c129e164fd0..8a39fc5261125 100644
--- a/browser/components/urlbar/tests/browser/browser_searchHistoryLimit.js
+++ b/browser/components/urlbar/tests/browser/browser_searchHistoryLimit.js
@@ -15,7 +15,7 @@ const { SearchSuggestionController } = ChromeUtils.import(
 
 let gEngine;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SearchTestUtils.installSearchExtension();
   gEngine = Services.search.getEngineByName("Example");
   let oldDefaultEngine = await Services.search.getDefault();
diff --git a/browser/components/urlbar/tests/browser/browser_searchMode_alias_replacement.js b/browser/components/urlbar/tests/browser/browser_searchMode_alias_replacement.js
index 397b7585f22ad..7cdb2f2a8f3a6 100644
--- a/browser/components/urlbar/tests/browser/browser_searchMode_alias_replacement.js
+++ b/browser/components/urlbar/tests/browser/browser_searchMode_alias_replacement.js
@@ -18,7 +18,7 @@ const TEST_SPACES = [" ", "\u3000", " \u3000", "\u3000 "];
 
 let defaultEngine, aliasEngine;
 
-add_task(async function setup() {
+add_setup(async function() {
   defaultEngine = await SearchTestUtils.promiseNewSearchEngine(
     getRootDirectory(gTestPath) + TEST_ENGINE_BASENAME
   );
diff --git a/browser/components/urlbar/tests/browser/browser_searchMode_autofill.js b/browser/components/urlbar/tests/browser/browser_searchMode_autofill.js
index 037cbcfd8aa76..36838e8f5834a 100644
--- a/browser/components/urlbar/tests/browser/browser_searchMode_autofill.js
+++ b/browser/components/urlbar/tests/browser/browser_searchMode_autofill.js
@@ -8,7 +8,7 @@
 
 "use strict";
 
-add_task(async function setup() {
+add_setup(async function() {
   for (let i = 0; i < 5; i++) {
     await PlacesTestUtils.addVisits([{ uri: "http://example.com/" }]);
   }
diff --git a/browser/components/urlbar/tests/browser/browser_searchMode_excludeResults.js b/browser/components/urlbar/tests/browser/browser_searchMode_excludeResults.js
index 8063c991ff879..9ea58d9e5686b 100644
--- a/browser/components/urlbar/tests/browser/browser_searchMode_excludeResults.js
+++ b/browser/components/urlbar/tests/browser/browser_searchMode_excludeResults.js
@@ -12,7 +12,7 @@ XPCOMUtils.defineLazyModuleGetters(this, {
   SyncedTabs: "resource://services-sync/SyncedTabs.jsm",
 });
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.urlbar.suggest.searches", false],
diff --git a/browser/components/urlbar/tests/browser/browser_searchMode_heuristic.js b/browser/components/urlbar/tests/browser/browser_searchMode_heuristic.js
index bb2ec593f711a..7cf7942b42ef9 100644
--- a/browser/components/urlbar/tests/browser/browser_searchMode_heuristic.js
+++ b/browser/components/urlbar/tests/browser/browser_searchMode_heuristic.js
@@ -7,7 +7,7 @@
 
 "use strict";
 
-add_task(async function setup() {
+add_setup(async function() {
   await PlacesUtils.history.clear();
   await PlacesUtils.bookmarks.eraseEverything();
 
diff --git a/browser/components/urlbar/tests/browser/browser_searchMode_indicator.js b/browser/components/urlbar/tests/browser/browser_searchMode_indicator.js
index 7b8defc4d2daf..b4a755b95a8a6 100644
--- a/browser/components/urlbar/tests/browser/browser_searchMode_indicator.js
+++ b/browser/components/urlbar/tests/browser/browser_searchMode_indicator.js
@@ -22,7 +22,7 @@ const TOP_SITES_URLS = [
 let suggestionsEngine;
 let defaultEngine;
 
-add_task(async function setup() {
+add_setup(async function() {
   suggestionsEngine = await SearchTestUtils.promiseNewSearchEngine(
     getRootDirectory(gTestPath) + SUGGESTIONS_ENGINE_NAME
   );
diff --git a/browser/components/urlbar/tests/browser/browser_searchMode_localOneOffs_actionText.js b/browser/components/urlbar/tests/browser/browser_searchMode_localOneOffs_actionText.js
index c4c5f271c2b5f..705734d66025b 100644
--- a/browser/components/urlbar/tests/browser/browser_searchMode_localOneOffs_actionText.js
+++ b/browser/components/urlbar/tests/browser/browser_searchMode_localOneOffs_actionText.js
@@ -13,7 +13,7 @@ const SUGGESTIONS_ENGINE_NAME = "searchSuggestionEngine.xml";
 
 let engine;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["browser.urlbar.suggest.searches", true]],
   });
diff --git a/browser/components/urlbar/tests/browser/browser_searchMode_no_results.js b/browser/components/urlbar/tests/browser/browser_searchMode_no_results.js
index 96da1d97218fd..fc2950051af32 100644
--- a/browser/components/urlbar/tests/browser/browser_searchMode_no_results.js
+++ b/browser/components/urlbar/tests/browser/browser_searchMode_no_results.js
@@ -9,7 +9,7 @@
 
 const TEST_ENGINE_BASENAME = "searchSuggestionEngine.xml";
 
-add_task(async function setup() {
+add_setup(async function() {
   // In order to open the view without any results, we need to be in search mode
   // with an empty search string so that no heuristic result is shown, and the
   // empty search must yield zero additional results.  We'll enter search mode
diff --git a/browser/components/urlbar/tests/browser/browser_searchMode_oneOffButton.js b/browser/components/urlbar/tests/browser/browser_searchMode_oneOffButton.js
index 1be595aadcf82..ae2e45bfed9e9 100644
--- a/browser/components/urlbar/tests/browser/browser_searchMode_oneOffButton.js
+++ b/browser/components/urlbar/tests/browser/browser_searchMode_oneOffButton.js
@@ -9,7 +9,7 @@
 
 const TEST_ENGINE_NAME = "test engine";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SearchTestUtils.installSearchExtension({
     name: TEST_ENGINE_NAME,
     keyword: "@test",
diff --git a/browser/components/urlbar/tests/browser/browser_searchMode_pickResult.js b/browser/components/urlbar/tests/browser/browser_searchMode_pickResult.js
index 98416ee10663f..97b58c5cafd5f 100644
--- a/browser/components/urlbar/tests/browser/browser_searchMode_pickResult.js
+++ b/browser/components/urlbar/tests/browser/browser_searchMode_pickResult.js
@@ -9,7 +9,7 @@
 
 const BOOKMARK_URL = "http://www.example.com/browser_searchMode_pickResult.js";
 
-add_task(async function setup() {
+add_setup(async function() {
   // Add a bookmark so we can enter bookmarks search mode and pick it.
   await PlacesUtils.bookmarks.eraseEverything();
   await PlacesUtils.bookmarks.insert({
diff --git a/browser/components/urlbar/tests/browser/browser_searchMode_preview.js b/browser/components/urlbar/tests/browser/browser_searchMode_preview.js
index 7ffc0868f5f76..2e9152bf20469 100644
--- a/browser/components/urlbar/tests/browser/browser_searchMode_preview.js
+++ b/browser/components/urlbar/tests/browser/browser_searchMode_preview.js
@@ -11,7 +11,7 @@ const TEST_ENGINE_NAME = "Test";
 
 let win;
 
-add_task(async function setup() {
+add_setup(async function() {
   win = await BrowserTestUtils.openNewBrowserWindow();
 
   await SearchTestUtils.installSearchExtension({
diff --git a/browser/components/urlbar/tests/browser/browser_searchMode_suggestions.js b/browser/components/urlbar/tests/browser/browser_searchMode_suggestions.js
index 86fc1ddff1a01..f7b6fabf54abb 100644
--- a/browser/components/urlbar/tests/browser/browser_searchMode_suggestions.js
+++ b/browser/components/urlbar/tests/browser/browser_searchMode_suggestions.js
@@ -15,7 +15,7 @@ const MAX_RESULT_COUNT = UrlbarPrefs.get("maxRichResults");
 let suggestionsEngine;
 let expectedFormHistoryResults = [];
 
-add_task(async function setup() {
+add_setup(async function() {
   suggestionsEngine = await SearchTestUtils.promiseNewSearchEngine(
     getRootDirectory(gTestPath) + SUGGESTIONS_ENGINE_NAME
   );
diff --git a/browser/components/urlbar/tests/browser/browser_searchSingleWordNotification.js b/browser/components/urlbar/tests/browser/browser_searchSingleWordNotification.js
index 0ee9f771ea182..47225e614b53b 100644
--- a/browser/components/urlbar/tests/browser/browser_searchSingleWordNotification.js
+++ b/browser/components/urlbar/tests/browser/browser_searchSingleWordNotification.js
@@ -3,7 +3,7 @@
 
 let gDNSResolved = false;
 let gRealDNSService = gDNSService;
-add_task(async function setup() {
+add_setup(async function() {
   gDNSService = {
     asyncResolve() {
       gDNSResolved = true;
diff --git a/browser/components/urlbar/tests/browser/browser_separatePrivateDefault.js b/browser/components/urlbar/tests/browser/browser_separatePrivateDefault.js
index 5f6a709e4ef3e..ba5b99f0b8dab 100644
--- a/browser/components/urlbar/tests/browser/browser_separatePrivateDefault.js
+++ b/browser/components/urlbar/tests/browser/browser_separatePrivateDefault.js
@@ -13,7 +13,7 @@ const serverInfo = {
   port: 20709, // Must be identical to what is in searchSuggestionEngine2.xml
 };
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.search.separatePrivateDefault.ui.enabled", true],
diff --git a/browser/components/urlbar/tests/browser/browser_separatePrivateDefault_differentEngine.js b/browser/components/urlbar/tests/browser/browser_separatePrivateDefault_differentEngine.js
index d422e6191461f..ca6216be98e61 100644
--- a/browser/components/urlbar/tests/browser/browser_separatePrivateDefault_differentEngine.js
+++ b/browser/components/urlbar/tests/browser/browser_separatePrivateDefault_differentEngine.js
@@ -14,7 +14,7 @@ const serverInfo = {
 let gAliasEngine;
 let gPrivateEngine;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.search.separatePrivateDefault.ui.enabled", true],
diff --git a/browser/components/urlbar/tests/browser/browser_shortcuts_add_search_engine.js b/browser/components/urlbar/tests/browser/browser_shortcuts_add_search_engine.js
index 1d950f00759b1..717518ed42199 100644
--- a/browser/components/urlbar/tests/browser/browser_shortcuts_add_search_engine.js
+++ b/browser/components/urlbar/tests/browser/browser_shortcuts_add_search_engine.js
@@ -13,7 +13,7 @@ const { PromptTestUtils } = ChromeUtils.import(
 const BASE_URL =
   "http://mochi.test:8888/browser/browser/components/urlbar/tests/browser/";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["browser.urlbar.suggest.searches", false]],
   });
diff --git a/browser/components/urlbar/tests/browser/browser_speculative_connect.js b/browser/components/urlbar/tests/browser/browser_speculative_connect.js
index 2b4d132812442..1af1c18bb93fd 100644
--- a/browser/components/urlbar/tests/browser/browser_speculative_connect.js
+++ b/browser/components/urlbar/tests/browser/browser_speculative_connect.js
@@ -17,7 +17,7 @@ const serverInfo = {
   port: 20709, // Must be identical to what is in searchSuggestionEngine2.xml
 };
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.urlbar.autoFill", true],
diff --git a/browser/components/urlbar/tests/browser/browser_speculative_connect_not_with_client_cert.js b/browser/components/urlbar/tests/browser/browser_speculative_connect_not_with_client_cert.js
index 0dc7e2667214c..72b9130699a47 100644
--- a/browser/components/urlbar/tests/browser/browser_speculative_connect_not_with_client_cert.js
+++ b/browser/components/urlbar/tests/browser/browser_speculative_connect_not_with_client_cert.js
@@ -118,7 +118,7 @@ function startServer(cert) {
 
 let server;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.urlbar.autoFill", true],
diff --git a/browser/components/urlbar/tests/browser/browser_suppressFocusBorder.js b/browser/components/urlbar/tests/browser/browser_suppressFocusBorder.js
index c29cd56d80bb9..20038d837ceb6 100644
--- a/browser/components/urlbar/tests/browser/browser_suppressFocusBorder.js
+++ b/browser/components/urlbar/tests/browser/browser_suppressFocusBorder.js
@@ -37,7 +37,7 @@ class AwaitPromiseProvider extends UrlbarTestUtils.TestProvider {
   }
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SearchTestUtils.installSearchExtension();
   let engine = Services.search.getEngineByName("Example");
   let oldDefaultEngine = Services.search.defaultEngine;
diff --git a/browser/components/urlbar/tests/browser/browser_switchTab_inputHistory.js b/browser/components/urlbar/tests/browser/browser_switchTab_inputHistory.js
index 4110ff0b38df1..943a8eb050e65 100644
--- a/browser/components/urlbar/tests/browser/browser_switchTab_inputHistory.js
+++ b/browser/components/urlbar/tests/browser/browser_switchTab_inputHistory.js
@@ -8,7 +8,7 @@
 
 "use strict";
 
-add_task(async function setup() {
+add_setup(async function() {
   registerCleanupFunction(async () => {
     await PlacesUtils.history.clear();
   });
diff --git a/browser/components/urlbar/tests/browser/browser_tabToSearch.js b/browser/components/urlbar/tests/browser/browser_tabToSearch.js
index 5bff9c1054bdb..93f38b089e57e 100644
--- a/browser/components/urlbar/tests/browser/browser_tabToSearch.js
+++ b/browser/components/urlbar/tests/browser/browser_tabToSearch.js
@@ -18,7 +18,7 @@ XPCOMUtils.defineLazyModuleGetters(this, {
     "resource:///modules/UrlbarProviderTabToSearch.jsm",
 });
 
-add_task(async function setup() {
+add_setup(async function() {
   await PlacesUtils.history.clear();
   await SpecialPowers.pushPrefEnv({
     set: [
diff --git a/browser/components/urlbar/tests/browser/browser_typed_value.js b/browser/components/urlbar/tests/browser/browser_typed_value.js
index a01ee3e08eef9..cd3b107e0859a 100644
--- a/browser/components/urlbar/tests/browser/browser_typed_value.js
+++ b/browser/components/urlbar/tests/browser/browser_typed_value.js
@@ -5,7 +5,7 @@
 
 "use strict";
 
-add_task(async function setup() {
+add_setup(async function() {
   registerCleanupFunction(async function() {
     Services.prefs.clearUserPref("browser.urlbar.autoFill");
     gURLBar.handleRevert();
diff --git a/browser/components/urlbar/tests/browser/browser_unitConversion.js b/browser/components/urlbar/tests/browser/browser_unitConversion.js
index 7a877ef56dcec..ab057c8241e89 100644
--- a/browser/components/urlbar/tests/browser/browser_unitConversion.js
+++ b/browser/components/urlbar/tests/browser/browser_unitConversion.js
@@ -7,7 +7,7 @@
  * Tests unit conversion on browser.
  */
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["browser.urlbar.unitConversion.enabled", true]],
   });
diff --git a/browser/components/urlbar/tests/browser/browser_urlbar_selection.js b/browser/components/urlbar/tests/browser/browser_urlbar_selection.js
index e890ed17cf493..23d942630191a 100644
--- a/browser/components/urlbar/tests/browser/browser_urlbar_selection.js
+++ b/browser/components/urlbar/tests/browser/browser_urlbar_selection.js
@@ -82,7 +82,7 @@ function checkPrimarySelection(expectedVal = "") {
   }
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // On macOS, we must "warm up" the Urlbar to get the first test to pass.
   gURLBar.value = "";
   await click(gURLBar.inputField);
diff --git a/browser/components/urlbar/tests/browser/browser_urlbar_telemetry.js b/browser/components/urlbar/tests/browser/browser_urlbar_telemetry.js
index f6eb0fb407554..5682426fe7943 100644
--- a/browser/components/urlbar/tests/browser/browser_urlbar_telemetry.js
+++ b/browser/components/urlbar/tests/browser/browser_urlbar_telemetry.js
@@ -86,7 +86,7 @@ async function withNewSearchEngine(taskFn) {
   }
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SearchTestUtils.installSearchExtension({
     name: "MozSearch",
     keyword: "mozalias",
diff --git a/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_extension.js b/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_extension.js
index 19bebf8918194..2e728fff55712 100644
--- a/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_extension.js
+++ b/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_extension.js
@@ -94,7 +94,7 @@ function assertTelemetryResults(histograms, type, index, method) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       // Disable search suggestions in the urlbar.
diff --git a/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_handoff.js b/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_handoff.js
index 234e4b90f38e7..97b9d454839f8 100644
--- a/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_handoff.js
+++ b/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_handoff.js
@@ -33,7 +33,7 @@ async function waitForIdle() {
   }
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   SearchSERPTelemetry.overrideSearchTelemetryForTests(TEST_PROVIDER_INFO);
   await waitForIdle();
 
diff --git a/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_places.js b/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_places.js
index ed69500afc468..800db9f4dc264 100644
--- a/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_places.js
+++ b/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_places.js
@@ -109,7 +109,7 @@ function assertTelemetryResults(histograms, type, index, method) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       // Disable search suggestions in the urlbar.
diff --git a/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_remotetab.js b/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_remotetab.js
index 38585316c1c97..886e372ee1e28 100644
--- a/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_remotetab.js
+++ b/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_remotetab.js
@@ -95,7 +95,7 @@ function assertTelemetryResults(histograms, type, index, method) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       // Disable search suggestions in the urlbar.
diff --git a/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_searchmode.js b/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_searchmode.js
index 0b2f047f1b852..c3fdca3ffc1d1 100644
--- a/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_searchmode.js
+++ b/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_searchmode.js
@@ -82,7 +82,7 @@ function assertSearchModeScalars(entry, engineOrSource, resultIndex = -1) {
   Services.telemetry.clearEvents();
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       // Disable tab-to-search onboarding results for general tests. They are
diff --git a/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_sponsored_topsites.js b/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_sponsored_topsites.js
index 8d580abb78d73..71a7ceaa51c4c 100644
--- a/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_sponsored_topsites.js
+++ b/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_sponsored_topsites.js
@@ -26,7 +26,7 @@ function submitHandler(request, response) {
 // Spy for telemetry sender
 let spy;
 
-add_task(async function setup() {
+add_setup(async function() {
   sandbox = sinon.createSandbox();
   spy = sandbox.spy(
     PartnerLinkAttribution._pingCentre,
diff --git a/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_tabtosearch.js b/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_tabtosearch.js
index f50d6f4a7cc88..d69e1b1f62357 100644
--- a/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_tabtosearch.js
+++ b/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_tabtosearch.js
@@ -103,7 +103,7 @@ async function checkForTabToSearchResult(engineName, isOnboarding) {
   }
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["browser.urlbar.tabToSearch.onboard.interactionsLeft", 0]],
   });
diff --git a/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_tip.js b/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_tip.js
index a23fffdb3fafc..74770844b2893 100644
--- a/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_tip.js
+++ b/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_tip.js
@@ -61,7 +61,7 @@ function assertTelemetryResults(histograms, type, index, method) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       // Disable search suggestions in the urlbar.
diff --git a/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_topsite.js b/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_topsite.js
index 352e08cf8f5a5..6759b2cffbf92 100644
--- a/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_topsite.js
+++ b/browser/components/urlbar/tests/browser/browser_urlbar_telemetry_topsite.js
@@ -89,7 +89,7 @@ async function updateTopSites(condition, searchShortcuts = false) {
   }, "Waiting for top sites to be updated");
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.urlbar.suggest.topsites", true],
diff --git a/browser/components/urlbar/tests/browser/browser_view_resultDisplay.js b/browser/components/urlbar/tests/browser/browser_view_resultDisplay.js
index 63de1909355d0..1cf6d3be29769 100644
--- a/browser/components/urlbar/tests/browser/browser_view_resultDisplay.js
+++ b/browser/components/urlbar/tests/browser/browser_view_resultDisplay.js
@@ -8,7 +8,7 @@
  * we expect them to be.
  */
 
-add_task(async function setup() {
+add_setup(async function() {
   await PlacesUtils.history.clear();
 
   registerCleanupFunction(async function() {
diff --git a/browser/components/urlbar/tests/browser/browser_view_resultTypes_display.js b/browser/components/urlbar/tests/browser/browser_view_resultTypes_display.js
index 05d5de2408d51..e2d150d74f12a 100644
--- a/browser/components/urlbar/tests/browser/browser_view_resultTypes_display.js
+++ b/browser/components/urlbar/tests/browser/browser_view_resultTypes_display.js
@@ -30,7 +30,7 @@ function assertElementsDisplayed(details, expected) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.urlbar.suggest.searches", false],
diff --git a/browser/components/urlbar/tests/quicksuggest/browser/browser_quicksuggest_onboardingDialog.js b/browser/components/urlbar/tests/quicksuggest/browser/browser_quicksuggest_onboardingDialog.js
index 07c0fd67487c9..f3eda4b651f17 100644
--- a/browser/components/urlbar/tests/quicksuggest/browser/browser_quicksuggest_onboardingDialog.js
+++ b/browser/components/urlbar/tests/quicksuggest/browser/browser_quicksuggest_onboardingDialog.js
@@ -32,7 +32,7 @@ if (AppConstants.platform == "macosx") {
 // Whether the tab key can move the focus. On macOS with full keyboard access
 // disabled (which is default), this will be false. See `canTabMoveFocus`.
 let gCanTabMoveFocus;
-add_task(async function setup() {
+add_setup(async function() {
   gCanTabMoveFocus = await canTabMoveFocus();
 });
 
diff --git a/browser/extensions/formautofill/test/browser/creditCard/browser_editCreditCardDialog.js b/browser/extensions/formautofill/test/browser/creditCard/browser_editCreditCardDialog.js
index e724ee4e2918f..7d2e081a73111 100644
--- a/browser/extensions/formautofill/test/browser/creditCard/browser_editCreditCardDialog.js
+++ b/browser/extensions/formautofill/test/browser/creditCard/browser_editCreditCardDialog.js
@@ -2,7 +2,7 @@
 
 "use strict";
 
-add_task(async function setup() {
+add_setup(async function() {
   let { formAutofillStorage } = ChromeUtils.import(
     "resource://autofill/FormAutofillStorage.jsm"
   );
diff --git a/browser/extensions/formautofill/test/browser/head.js b/browser/extensions/formautofill/test/browser/head.js
index 709f6b904a401..7bee7b7dc8fd6 100644
--- a/browser/extensions/formautofill/test/browser/head.js
+++ b/browser/extensions/formautofill/test/browser/head.js
@@ -732,7 +732,7 @@ async function testDialog(url, testFn, arg = undefined) {
   return unloadPromise;
 }
 
-add_task(function setup() {
+add_setup(function() {
   OSKeyStoreTestUtils.setup();
 });
 
diff --git a/browser/extensions/search-detection/tests/browser/browser_client_side_redirection.js b/browser/extensions/search-detection/tests/browser/browser_client_side_redirection.js
index 13720926ed626..05cc207f436a0 100644
--- a/browser/extensions/search-detection/tests/browser/browser_client_side_redirection.js
+++ b/browser/extensions/search-detection/tests/browser/browser_client_side_redirection.js
@@ -78,7 +78,7 @@ async function testClientSideRedirect({
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   const searchEngineName = "test search engine";
 
   let searchEngine;
diff --git a/browser/extensions/webcompat/tests/browser/browser_shims.js b/browser/extensions/webcompat/tests/browser/browser_shims.js
index cd07bb7390eed..87604c0a6fd81 100644
--- a/browser/extensions/webcompat/tests/browser/browser_shims.js
+++ b/browser/extensions/webcompat/tests/browser/browser_shims.js
@@ -5,7 +5,7 @@ registerCleanupFunction(() => {
   Services.prefs.clearUserPref(TRACKING_PREF);
 });
 
-add_task(async function setup() {
+add_setup(async function() {
   await UrlClassifierTestUtils.addTestTrackers();
 });
 
diff --git a/browser/modules/test/browser/browser_ContentSearch.js b/browser/modules/test/browser/browser_ContentSearch.js
index a3c26cbff1fba..adb26cf7e6eff 100644
--- a/browser/modules/test/browser/browser_ContentSearch.js
+++ b/browser/modules/test/browser/browser_ContentSearch.js
@@ -30,7 +30,7 @@ function sendEventToContent(browser, data) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   const originalEngine = await Services.search.getDefault();
   const originalPrivateEngine = await Services.search.getDefaultPrivate();
 
diff --git a/browser/modules/test/browser/browser_PartnerLinkAttribution.js b/browser/modules/test/browser/browser_PartnerLinkAttribution.js
index 1f27bcba8b800..b9732798ade28 100644
--- a/browser/modules/test/browser/browser_PartnerLinkAttribution.js
+++ b/browser/modules/test/browser/browser_PartnerLinkAttribution.js
@@ -36,7 +36,7 @@ function submitHandler(request, response) {
   response.setStatusLine(request.httpVersion, 200, "Ok");
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // Ensure the initial init is complete.
   await Services.search.init();
 
diff --git a/browser/modules/test/browser/browser_ProcessHangNotifications.js b/browser/modules/test/browser/browser_ProcessHangNotifications.js
index 44aa98b64680d..f0a770407d141 100644
--- a/browser/modules/test/browser/browser_ProcessHangNotifications.js
+++ b/browser/modules/test/browser/browser_ProcessHangNotifications.js
@@ -106,7 +106,7 @@ TestHangReport.prototype = {
 // on dev edition we add a button for js debugging of hung scripts.
 let buttonCount = AppConstants.MOZ_DEV_EDITION ? 2 : 1;
 
-add_task(async function setup() {
+add_setup(async function() {
   // Create a fake WebExtensionPolicy that we can use for
   // the add-on hang notification.
   const uuidGen = Services.uuid;
diff --git a/browser/modules/test/browser/browser_UnsubmittedCrashHandler.js b/browser/modules/test/browser/browser_UnsubmittedCrashHandler.js
index c3a613b04a218..40a6dbd1113df 100644
--- a/browser/modules/test/browser/browser_UnsubmittedCrashHandler.js
+++ b/browser/modules/test/browser/browser_UnsubmittedCrashHandler.js
@@ -197,7 +197,7 @@ function waitForIgnoredReports(reportIDs) {
   return Promise.all(promises);
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // Pending crash reports are stored in the UAppData folder,
   // which exists outside of the profile folder. In order to
   // not overwrite / clear pending crash reports for the poor
diff --git a/devtools/client/performance-new/test/browser/browser_split-toolbar-button.js b/devtools/client/performance-new/test/browser/browser_split-toolbar-button.js
index f923675370376..cb38e675e9f57 100644
--- a/devtools/client/performance-new/test/browser/browser_split-toolbar-button.js
+++ b/devtools/client/performance-new/test/browser/browser_split-toolbar-button.js
@@ -39,7 +39,7 @@ async function waitForProfileAndCloseTab() {
 var button;
 var dropmarker;
 
-add_task(async function setup() {
+add_setup(async function() {
   info(
     "Add the profiler button to the toolbar and ensure capturing a profile loads a local url."
   );
diff --git a/devtools/server/tests/browser/browser_animation_actor-lifetime.js b/devtools/server/tests/browser/browser_animation_actor-lifetime.js
index c8c4fce119eaf..3e117b263bc48 100644
--- a/devtools/server/tests/browser/browser_animation_actor-lifetime.js
+++ b/devtools/server/tests/browser/browser_animation_actor-lifetime.js
@@ -5,7 +5,7 @@
 
 // Test for Bug 1247243
 
-add_task(async function setup() {
+add_setup(async function() {
   info("Setting up inspector and animation actors.");
   const { animations, walker } = await initAnimationsFrontForUrl(
     MAIN_DOMAIN + "animation-data.html"
diff --git a/devtools/server/tests/browser/browser_inspector-insert.js b/devtools/server/tests/browser/browser_inspector-insert.js
index b5b55c2d63b42..c2a5a55b6ed0c 100644
--- a/devtools/server/tests/browser/browser_inspector-insert.js
+++ b/devtools/server/tests/browser/browser_inspector-insert.js
@@ -3,7 +3,7 @@
 
 "use strict";
 
-add_task(async function setup() {
+add_setup(async function() {
   const { walker } = await initInspectorFront(
     MAIN_DOMAIN + "inspector-traversal-data.html"
   );
diff --git a/docshell/test/browser/browser_data_load_inherit_csp.js b/docshell/test/browser/browser_data_load_inherit_csp.js
index 806803d2b5191..17d9ad9e16e23 100644
--- a/docshell/test/browser/browser_data_load_inherit_csp.js
+++ b/docshell/test/browser/browser_data_load_inherit_csp.js
@@ -35,7 +35,7 @@ function verifyCSP(aTestName, aBrowser, aDataURI) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // allow top level data: URI navigations, otherwise clicking data: link fails
   await SpecialPowers.pushPrefEnv({
     set: [["security.data_uri.block_toplevel_data_uri_navigations", false]],
diff --git a/docshell/test/browser/browser_uriFixupIntegration.js b/docshell/test/browser/browser_uriFixupIntegration.js
index a2c4e362abe6d..e5530742e101f 100644
--- a/docshell/test/browser/browser_uriFixupIntegration.js
+++ b/docshell/test/browser/browser_uriFixupIntegration.js
@@ -17,7 +17,7 @@ const kSearchEngineURL = "https://example.com/?search={searchTerms}";
 const kPrivateSearchEngineID = "browser_urifixup_search_engine_private";
 const kPrivateSearchEngineURL = "https://example.com/?private={searchTerms}";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.search.separatePrivateDefault.ui.enabled", true],
diff --git a/dom/base/test/browser_promiseDocumentFlushed.js b/dom/base/test/browser_promiseDocumentFlushed.js
index 2dbd47cc7d46c..a3fc93cf88f4d 100644
--- a/dom/base/test/browser_promiseDocumentFlushed.js
+++ b/dom/base/test/browser_promiseDocumentFlushed.js
@@ -64,7 +64,7 @@ async function cleanTheDOM() {
   await window.promiseDocumentFlushed(() => {});
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   registerCleanupFunction(cleanTheDOM);
 });
 
diff --git a/dom/base/test/browser_timeout_throttling_with_audio_playback.js b/dom/base/test/browser_timeout_throttling_with_audio_playback.js
index 6f952949088e9..c859dd3dc2136 100644
--- a/dom/base/test/browser_timeout_throttling_with_audio_playback.js
+++ b/dom/base/test/browser_timeout_throttling_with_audio_playback.js
@@ -58,7 +58,7 @@ async function runTest(url) {
   BrowserTestUtils.removeTab(newTab);
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["dom.min_background_timeout_value", kMinTimeoutBackground]],
   });
diff --git a/dom/base/test/chrome/test_fileconstructor.xhtml b/dom/base/test/chrome/test_fileconstructor.xhtml
index cc4f3f47641ec..709ecad8fab93 100644
--- a/dom/base/test/chrome/test_fileconstructor.xhtml
+++ b/dom/base/test/chrome/test_fileconstructor.xhtml
@@ -30,6 +30,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=607114.xul
 
 /** Test for Bug 607114 **/
 
+// eslint-disable-next-line mozilla/no-addtask-setup
 add_task(async function setup() {
   await SpecialPowers.pushPrefEnv({ set: [[ "dom.file.createInChild", true ]]});
 });
diff --git a/dom/events/test/pointerevents/test_multiple_touches.html b/dom/events/test/pointerevents/test_multiple_touches.html
index f17d07f137c61..b316c79000d2a 100644
--- a/dom/events/test/pointerevents/test_multiple_touches.html
+++ b/dom/events/test/pointerevents/test_multiple_touches.html
@@ -129,6 +129,7 @@
   return promise;
 }
 
+// eslint-disable-next-line mozilla/no-addtask-setup
 add_task(async function setup() {
   await SimpleTest.promiseFocus();
   await SpecialPowers.pushPrefEnv({
diff --git a/dom/html/test/test_bug1322678.html b/dom/html/test/test_bug1322678.html
index f05da46d4d731..57b43f039c0bd 100644
--- a/dom/html/test/test_bug1322678.html
+++ b/dom/html/test/test_bug1322678.html
@@ -72,6 +72,7 @@
   });
 }
 
+// eslint-disable-next-line mozilla/no-addtask-setup
 add_task(async function setup() {
   await SpecialPowers.pushPrefEnv({"set": [
     ["browser.enable_automatic_image_resizing", true],
diff --git a/dom/html/test/test_inputmode.html b/dom/html/test/test_inputmode.html
index f38b2b21302ce..56bb101e8a3af 100644
--- a/dom/html/test/test_inputmode.html
+++ b/dom/html/test/test_inputmode.html
@@ -44,6 +44,7 @@
 </div>
 <pre id="test">
 <script class=testbody" type="application/javascript">
+// eslint-disable-next-line mozilla/no-addtask-setup
 add_task(async function setup() {
   await new Promise(r => SimpleTest.waitForFocus(r));
 });
diff --git a/dom/ipc/tests/browser_ProcessPriorityManager.js b/dom/ipc/tests/browser_ProcessPriorityManager.js
index 99fc801c70819..63cd5d3e1990a 100644
--- a/dom/ipc/tests/browser_ProcessPriorityManager.js
+++ b/dom/ipc/tests/browser_ProcessPriorityManager.js
@@ -207,7 +207,7 @@ class TabPriorityWatcher {
 
 let gTabPriorityWatcher;
 
-add_task(async function setup() {
+add_setup(async function() {
   // We need to turn on testMode for the process priority manager in
   // order to receive the observer notifications that this test relies on.
   await SpecialPowers.pushPrefEnv({
diff --git a/dom/ipc/tests/browser_domainPolicy.js b/dom/ipc/tests/browser_domainPolicy.js
index cec360f2e14f5..d626966b27b69 100644
--- a/dom/ipc/tests/browser_domainPolicy.js
+++ b/dom/ipc/tests/browser_domainPolicy.js
@@ -55,7 +55,7 @@ function deactivateDomainPolicy() {
   }
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["browser.pagethumbnails.capturing_disabled", false]],
   });
diff --git a/dom/ipc/tests/test_sharedMap.js b/dom/ipc/tests/test_sharedMap.js
index 5b66841e55ef0..4fb1548e7806c 100644
--- a/dom/ipc/tests/test_sharedMap.js
+++ b/dom/ipc/tests/test_sharedMap.js
@@ -113,7 +113,7 @@ async function loadContentPage() {
   return page;
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // Start with one content process so that we can increase the number
   // later and test the behavior of a fresh content process.
   Services.prefs.setIntPref(PROCESS_COUNT_PREF, 1);
diff --git a/dom/notification/test/browser/browser_permission_dismiss.js b/dom/notification/test/browser/browser_permission_dismiss.js
index e5a95fb3bd6fb..f5eb04cba86e9 100644
--- a/dom/notification/test/browser/browser_permission_dismiss.js
+++ b/dom/notification/test/browser/browser_permission_dismiss.js
@@ -93,7 +93,7 @@ function tabWithRequest(task, permission) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   Services.prefs.setBoolPref(
     "dom.webnotifications.requireuserinteraction",
     false
diff --git a/dom/security/test/general/browser_test_assert_systemprincipal_documents.js b/dom/security/test/general/browser_test_assert_systemprincipal_documents.js
index 25fb2db7355d2..08abdb77051e4 100644
--- a/dom/security/test/general/browser_test_assert_systemprincipal_documents.js
+++ b/dom/security/test/general/browser_test_assert_systemprincipal_documents.js
@@ -3,7 +3,7 @@
 const kTestPath = getRootDirectory(gTestPath);
 const kTestURI = kTestPath + "file_assert_systemprincipal_documents.html";
 
-add_task(async function setup() {
+add_setup(async function() {
   // We expect the assertion in function
   // CheckSystemPrincipalLoads as defined in
   // file dom/security/nsContentSecurityManager.cpp
diff --git a/dom/security/test/general/browser_test_report_blocking.js b/dom/security/test/general/browser_test_report_blocking.js
index 43d15e7c8ef0d..39ea8bea44785 100644
--- a/dom/security/test/general/browser_test_report_blocking.js
+++ b/dom/security/test/general/browser_test_report_blocking.js
@@ -62,7 +62,7 @@ const TEST_CASES = [
   },
 ];
 
-add_task(async function setup() {
+add_setup(async function() {
   Services.telemetry.setEventRecordingEnabled("security.ui.xfocsperror", true);
 
   await SpecialPowers.pushPrefEnv({
diff --git a/dom/security/test/referrer-policy/browser_referrer_disallow_cross_site_relaxing.js b/dom/security/test/referrer-policy/browser_referrer_disallow_cross_site_relaxing.js
index 50b734be789b1..f924af51077e4 100644
--- a/dom/security/test/referrer-policy/browser_referrer_disallow_cross_site_relaxing.js
+++ b/dom/security/test/referrer-policy/browser_referrer_disallow_cross_site_relaxing.js
@@ -186,7 +186,7 @@ const TEST_CASES = [
   },
 ];
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       // Disable mixed content blocking to be able to test downgrade scenario.
diff --git a/dom/security/test/referrer-policy/browser_referrer_telemetry.js b/dom/security/test/referrer-policy/browser_referrer_telemetry.js
index bd5072d67d7c2..409c04c45ef47 100644
--- a/dom/security/test/referrer-policy/browser_referrer_telemetry.js
+++ b/dom/security/test/referrer-policy/browser_referrer_telemetry.js
@@ -69,7 +69,7 @@ function clearTelemetry() {
   Services.telemetry.getHistogramById("REFERRER_POLICY_COUNT").clear();
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // Clear Telemetry probes before testing.
   clearTelemetry();
 });
diff --git a/dom/serviceworkers/test/browser_storage_permission.js b/dom/serviceworkers/test/browser_storage_permission.js
index 4d9823c9e4af7..68c2c18bade9d 100644
--- a/dom/serviceworkers/test/browser_storage_permission.js
+++ b/dom/serviceworkers/test/browser_storage_permission.js
@@ -9,7 +9,7 @@ const PAGE_URI = BASE_URI + "empty.html";
 const SCOPE = PAGE_URI + "?storage_permission";
 const SW_SCRIPT = BASE_URI + "empty.js";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       // Until the e10s refactor is complete, use a single process to avoid
diff --git a/dom/serviceworkers/test/browser_storage_recovery.js b/dom/serviceworkers/test/browser_storage_recovery.js
index b06358adc1a5a..5ecc1350216fd 100644
--- a/dom/serviceworkers/test/browser_storage_recovery.js
+++ b/dom/serviceworkers/test/browser_storage_recovery.js
@@ -37,7 +37,7 @@ async function wipeStorage(u) {
   return Promise.all(list.map(c => caches.delete(c)));
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["dom.serviceWorkers.enabled", true],
diff --git a/dom/serviceworkers/test/browser_userContextId_openWindow.js b/dom/serviceworkers/test/browser_userContextId_openWindow.js
index 591d9a95748ac..ee191b1cbcf6b 100644
--- a/dom/serviceworkers/test/browser_userContextId_openWindow.js
+++ b/dom/serviceworkers/test/browser_userContextId_openWindow.js
@@ -59,7 +59,7 @@ registerCleanupFunction(() => {
   );
 });
 
-add_task(async function setup() {
+add_setup(async function() {
   // make sure userContext, SW and notifications are enabled.
   await SpecialPowers.pushPrefEnv({
     set: [
diff --git a/dom/serviceworkers/test/test_abrupt_completion.html b/dom/serviceworkers/test/test_abrupt_completion.html
index bb019c8134ea0..bbf9e965f0702 100644
--- a/dom/serviceworkers/test/test_abrupt_completion.html
+++ b/dom/serviceworkers/test/test_abrupt_completion.html
@@ -65,6 +65,7 @@
   });
 }
 
+// eslint-disable-next-line mozilla/no-addtask-setup
 add_task(async function setup() {
   await SpecialPowers.pushPrefEnv({
     set: [
diff --git a/dom/serviceworkers/test/test_notification_openWindow.html b/dom/serviceworkers/test/test_notification_openWindow.html
index 3e5a91c744b27..830c9e03d2b90 100644
--- a/dom/serviceworkers/test/test_notification_openWindow.html
+++ b/dom/serviceworkers/test/test_notification_openWindow.html
@@ -13,6 +13,7 @@
 <div id="content" style="display: none"></div>
 <pre id="test"></pre>
 <script class="testbody" type="text/javascript">
+// eslint-disable-next-line mozilla/no-addtask-setup
 add_task(async function setup() {
   await SpecialPowers.pushPrefEnv({"set": [
     ["dom.serviceWorkers.exemptFromPerDomainMax", true],
diff --git a/dom/serviceworkers/test/test_streamfilter.html b/dom/serviceworkers/test/test_streamfilter.html
index f4d7b155ac227..04d01db9a1609 100644
--- a/dom/serviceworkers/test/test_streamfilter.html
+++ b/dom/serviceworkers/test/test_streamfilter.html
@@ -11,6 +11,7 @@
 </head>
 <body>
 <script>
+// eslint-disable-next-line mozilla/no-addtask-setup
 add_task(async function setup() {
   SimpleTest.waitForExplicitFinish();
 
diff --git a/dom/tests/browser/browser_bug1685807.js b/dom/tests/browser/browser_bug1685807.js
index 493f93fea27f1..fc9aa3555b1dd 100644
--- a/dom/tests/browser/browser_bug1685807.js
+++ b/dom/tests/browser/browser_bug1685807.js
@@ -12,7 +12,7 @@ const EMPTY_URI =
 const TEST_URI =
   "https://test1.example.com/browser/dom/tests/browser/file_bug1685807.html";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["privacy.window.name.update.enabled", true]],
   });
diff --git a/dom/workers/test/browser_privilegedmozilla_remoteworker.js b/dom/workers/test/browser_privilegedmozilla_remoteworker.js
index d5e7befcdab78..012f029ac90f1 100644
--- a/dom/workers/test/browser_privilegedmozilla_remoteworker.js
+++ b/dom/workers/test/browser_privilegedmozilla_remoteworker.js
@@ -1,4 +1,4 @@
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.tabs.remote.separatePrivilegedMozillaWebContentProcess", true],
diff --git a/dom/workers/test/browser_serviceworker_fetch_new_process.js b/dom/workers/test/browser_serviceworker_fetch_new_process.js
index ccc93e3ce9ac9..db8ea3bba306a 100644
--- a/dom/workers/test/browser_serviceworker_fetch_new_process.js
+++ b/dom/workers/test/browser_serviceworker_fetch_new_process.js
@@ -9,7 +9,7 @@ const DIRPATH = getRootDirectory(gTestPath).replace(
  */
 const TEST_BLOB_CONTENTS = `I'm a disk-backed test blob! Hooray!`;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       // Set preferences so that opening a page with the origin "example.org"
diff --git a/dom/xhr/tests/browser_sync_xhr_event_handing_switch_bcg.js b/dom/xhr/tests/browser_sync_xhr_event_handing_switch_bcg.js
index becb22712dc96..bcfedeb93f215 100644
--- a/dom/xhr/tests/browser_sync_xhr_event_handing_switch_bcg.js
+++ b/dom/xhr/tests/browser_sync_xhr_event_handing_switch_bcg.js
@@ -6,7 +6,7 @@ const baseURL = getRootDirectory(gTestPath).replace(
 const childURL = `${baseURL}empty.html`;
 const parentURL = `${baseURL}empty_parent.html`;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["dom.input_events.canSuspendInBCG.enabled", true]],
   });
diff --git a/netwerk/cookie/test/browser/browser_originattributes.js b/netwerk/cookie/test/browser/browser_originattributes.js
index 7d43bc49f16bf..927c33dd2edf3 100644
--- a/netwerk/cookie/test/browser/browser_originattributes.js
+++ b/netwerk/cookie/test/browser/browser_originattributes.js
@@ -26,7 +26,7 @@ async function openTabInUserContext(uri, userContextId) {
   return { tab, browser };
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // make sure userContext is enabled.
   await new Promise(resolve => {
     SpecialPowers.pushPrefEnv(
diff --git a/netwerk/test/browser/browser_post_auth.js b/netwerk/test/browser/browser_post_auth.js
index 723d4c4f4fdfe..20bd867af93b5 100644
--- a/netwerk/test/browser/browser_post_auth.js
+++ b/netwerk/test/browser/browser_post_auth.js
@@ -22,7 +22,7 @@ const FOLDER = getRootDirectory(gTestPath).replace(
   "http://mochi.test:8888/"
 );
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     // https://bugzilla.mozilla.org/show_bug.cgi?id=1711676
     // Disable bfcache for Fission for now.
diff --git a/security/manager/ssl/tests/mochitest/browser/browser_clientAuth_connection.js b/security/manager/ssl/tests/mochitest/browser/browser_clientAuth_connection.js
index a0e9723f43166..272a622babe56 100644
--- a/security/manager/ssl/tests/mochitest/browser/browser_clientAuth_connection.js
+++ b/security/manager/ssl/tests/mochitest/browser/browser_clientAuth_connection.js
@@ -123,7 +123,7 @@ const gClientAuthDialogs = {
   QueryInterface: ChromeUtils.generateQI(["nsIClientAuthDialogs"]),
 };
 
-add_task(async function setup() {
+add_setup(async function() {
   let clientAuthDialogsCID = MockRegistrar.register(
     "@mozilla.org/nsClientAuthDialogs;1",
     gClientAuthDialogs
diff --git a/security/manager/ssl/tests/mochitest/browser/browser_clientAuth_ui.js b/security/manager/ssl/tests/mochitest/browser/browser_clientAuth_ui.js
index 243d1bb17414f..2b1b80376f8ff 100644
--- a/security/manager/ssl/tests/mochitest/browser/browser_clientAuth_ui.js
+++ b/security/manager/ssl/tests/mochitest/browser/browser_clientAuth_ui.js
@@ -135,7 +135,7 @@ function findCertByCommonName(commonName) {
   return null;
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   cert = findCertByCommonName("Mochitest client");
   isnot(cert, null, "Should be able to find the test client cert");
 });
diff --git a/security/manager/ssl/tests/mochitest/browser/browser_deleteCert_ui.js b/security/manager/ssl/tests/mochitest/browser/browser_deleteCert_ui.js
index 0d06c553a234f..3bb770894004d 100644
--- a/security/manager/ssl/tests/mochitest/browser/browser_deleteCert_ui.js
+++ b/security/manager/ssl/tests/mochitest/browser/browser_deleteCert_ui.js
@@ -101,7 +101,7 @@ function openDeleteCertConfirmDialog(tabID) {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   for (let testCase of TEST_CASES) {
     let cert = null;
     if (testCase.certFilename) {
diff --git a/security/manager/ssl/tests/mochitest/browser/browser_downloadCert_ui.js b/security/manager/ssl/tests/mochitest/browser/browser_downloadCert_ui.js
index 876124d5c253e..6e740c3734a13 100644
--- a/security/manager/ssl/tests/mochitest/browser/browser_downloadCert_ui.js
+++ b/security/manager/ssl/tests/mochitest/browser/browser_downloadCert_ui.js
@@ -66,7 +66,7 @@ function openCertDownloadDialog(cert) {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   for (let testCase of TEST_CASES) {
     testCase.cert = await readCertificate(testCase.certFilename, ",,");
     Assert.notEqual(
diff --git a/security/manager/ssl/tests/mochitest/browser/browser_editCACertTrust.js b/security/manager/ssl/tests/mochitest/browser/browser_editCACertTrust.js
index f4592ea9dcb8c..ecbb580e6e0cc 100644
--- a/security/manager/ssl/tests/mochitest/browser/browser_editCACertTrust.js
+++ b/security/manager/ssl/tests/mochitest/browser/browser_editCACertTrust.js
@@ -41,7 +41,7 @@ function openEditCertTrustDialog() {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // Initially trust ca.pem for SSL but not e-mail.
   gCert = await readCertificate("ca.pem", "CT,,");
   Assert.ok(
diff --git a/services/fxaccounts/tests/browser/browser_device_connected.js b/services/fxaccounts/tests/browser/browser_device_connected.js
index b2bcd9fa50ee1..267bd663e2138 100644
--- a/services/fxaccounts/tests/browser/browser_device_connected.js
+++ b/services/fxaccounts/tests/browser/browser_device_connected.js
@@ -15,7 +15,7 @@ const DEVICES_URL = "https://example.com/devices";
 
 let expectedBody;
 
-add_task(async function setup() {
+add_setup(async function() {
   const origManageDevicesURI = FxAccounts.config.promiseManageDevicesURI;
   FxAccounts.config.promiseManageDevicesURI = () =>
     Promise.resolve(DEVICES_URL);
diff --git a/toolkit/components/aboutconfig/test/browser/browser_accessibility.js b/toolkit/components/aboutconfig/test/browser/browser_accessibility.js
index 4cce4bfb50c59..fe2617d318b56 100644
--- a/toolkit/components/aboutconfig/test/browser/browser_accessibility.js
+++ b/toolkit/components/aboutconfig/test/browser/browser_accessibility.js
@@ -3,7 +3,7 @@
 
 const MAX_PLACEABLE_LENGTH = 2500;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["test.aboutconfig.added", "=".repeat(MAX_PLACEABLE_LENGTH)],
diff --git a/toolkit/components/aboutconfig/test/browser/browser_basic.js b/toolkit/components/aboutconfig/test/browser/browser_basic.js
index 57784985b0c95..70f2b7622fc14 100644
--- a/toolkit/components/aboutconfig/test/browser/browser_basic.js
+++ b/toolkit/components/aboutconfig/test/browser/browser_basic.js
@@ -1,7 +1,7 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       [
diff --git a/toolkit/components/aboutconfig/test/browser/browser_clipboard.js b/toolkit/components/aboutconfig/test/browser/browser_clipboard.js
index bead750e8c74c..24892446a9643 100644
--- a/toolkit/components/aboutconfig/test/browser/browser_clipboard.js
+++ b/toolkit/components/aboutconfig/test/browser/browser_clipboard.js
@@ -1,7 +1,7 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["test.aboutconfig.copy.false", false],
diff --git a/toolkit/components/aboutconfig/test/browser/browser_edit.js b/toolkit/components/aboutconfig/test/browser/browser_edit.js
index 9e8985afb93a8..aaf92b9e60510 100644
--- a/toolkit/components/aboutconfig/test/browser/browser_edit.js
+++ b/toolkit/components/aboutconfig/test/browser/browser_edit.js
@@ -6,7 +6,7 @@ const PREF_MODIFY_BOOLEAN = "test.aboutconfig.modify.boolean";
 const PREF_MODIFY_NUMBER = "test.aboutconfig.modify.number";
 const PREF_MODIFY_STRING = "test.aboutconfig.modify.string";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       [PREF_MODIFY_BOOLEAN, true],
diff --git a/toolkit/components/aboutconfig/test/browser/browser_locked.js b/toolkit/components/aboutconfig/test/browser/browser_locked.js
index 293855ae9bb97..fbc62cc4c4aa4 100644
--- a/toolkit/components/aboutconfig/test/browser/browser_locked.js
+++ b/toolkit/components/aboutconfig/test/browser/browser_locked.js
@@ -3,7 +3,7 @@
 
 const PREF_STRING_NO_DEFAULT = "test.aboutconfig.a";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [[PREF_STRING_NO_DEFAULT, "some value"]],
   });
diff --git a/toolkit/components/aboutconfig/test/browser/browser_observe.js b/toolkit/components/aboutconfig/test/browser/browser_observe.js
index 2782568b3389d..4474819c9dbf9 100644
--- a/toolkit/components/aboutconfig/test/browser/browser_observe.js
+++ b/toolkit/components/aboutconfig/test/browser/browser_observe.js
@@ -1,7 +1,7 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["test.aboutconfig.modify.boolean", true],
diff --git a/toolkit/components/aboutconfig/test/browser/browser_search.js b/toolkit/components/aboutconfig/test/browser/browser_search.js
index f0660f1665033..86b873fdaff12 100644
--- a/toolkit/components/aboutconfig/test/browser/browser_search.js
+++ b/toolkit/components/aboutconfig/test/browser/browser_search.js
@@ -1,7 +1,7 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["test.aboutconfig.a", "test value 1"],
diff --git a/toolkit/components/aboutconfig/test/browser/browser_warning.js b/toolkit/components/aboutconfig/test/browser/browser_warning.js
index c2ae6b551e9d6..f199d3e939d0e 100644
--- a/toolkit/components/aboutconfig/test/browser/browser_warning.js
+++ b/toolkit/components/aboutconfig/test/browser/browser_warning.js
@@ -1,7 +1,7 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["browser.aboutConfig.showWarning", true]],
   });
diff --git a/toolkit/components/aboutprocesses/tests/browser/browser_aboutprocesses_selection.js b/toolkit/components/aboutprocesses/tests/browser/browser_aboutprocesses_selection.js
index d6f80ae1fcb89..9f59e919ed438 100644
--- a/toolkit/components/aboutprocesses/tests/browser/browser_aboutprocesses_selection.js
+++ b/toolkit/components/aboutprocesses/tests/browser/browser_aboutprocesses_selection.js
@@ -16,7 +16,7 @@ function promiseUpdate() {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   Services.prefs.setBoolPref("toolkit.aboutProcesses.showThreads", true);
 
   info("Setting up about:processes");
diff --git a/toolkit/components/antitracking/test/browser/browser_AntiTrackingETPHeuristic.js b/toolkit/components/antitracking/test/browser/browser_AntiTrackingETPHeuristic.js
index ac78ed016ca44..8f131e1708bac 100644
--- a/toolkit/components/antitracking/test/browser/browser_AntiTrackingETPHeuristic.js
+++ b/toolkit/components/antitracking/test/browser/browser_AntiTrackingETPHeuristic.js
@@ -186,7 +186,7 @@ async function verifyStorageAccessPermission(aExpects) {
   }
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["network.cookie.cookieBehavior", BEHAVIOR_REJECT_TRACKER],
diff --git a/toolkit/components/antitracking/test/browser/browser_contentBlockingTelemetry.js b/toolkit/components/antitracking/test/browser/browser_contentBlockingTelemetry.js
index 4deada0f326f6..1e0088679da92 100644
--- a/toolkit/components/antitracking/test/browser/browser_contentBlockingTelemetry.js
+++ b/toolkit/components/antitracking/test/browser/browser_contentBlockingTelemetry.js
@@ -85,7 +85,7 @@ async function testTelemetry(
   clearTelemetry();
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["network.cookie.cookieBehavior", BEHAVIOR_REJECT_TRACKER],
diff --git a/toolkit/components/antitracking/test/browser/browser_fileUrl.js b/toolkit/components/antitracking/test/browser/browser_fileUrl.js
index 7702c941ea344..861c9b7e94381 100644
--- a/toolkit/components/antitracking/test/browser/browser_fileUrl.js
+++ b/toolkit/components/antitracking/test/browser/browser_fileUrl.js
@@ -5,7 +5,7 @@
 
 "use strict";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["network.cookie.cookieBehavior", 1],
diff --git a/toolkit/components/antitracking/test/browser/browser_iframe_document_open.js b/toolkit/components/antitracking/test/browser/browser_iframe_document_open.js
index e46fe96f05468..d3d27392db626 100644
--- a/toolkit/components/antitracking/test/browser/browser_iframe_document_open.js
+++ b/toolkit/components/antitracking/test/browser/browser_iframe_document_open.js
@@ -6,7 +6,7 @@
 
 const TEST_PAGE = TEST_DOMAIN + TEST_PATH + "file_iframe_document_open.html";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       [
diff --git a/toolkit/components/antitracking/test/browser/browser_partitionedClearSiteDataHeader.js b/toolkit/components/antitracking/test/browser/browser_partitionedClearSiteDataHeader.js
index 0c2cda0e1276c..d1d9829c893fd 100644
--- a/toolkit/components/antitracking/test/browser/browser_partitionedClearSiteDataHeader.js
+++ b/toolkit/components/antitracking/test/browser/browser_partitionedClearSiteDataHeader.js
@@ -371,7 +371,7 @@ async function setupInitialStorageState(storageType) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   info("Starting ClearSiteData test");
 
   await SpecialPowers.flushPrefEnv();
diff --git a/toolkit/components/antitracking/test/browser/browser_socialtracking_save_image.js b/toolkit/components/antitracking/test/browser/browser_socialtracking_save_image.js
index 75885722cb066..7c1dc91d92d68 100644
--- a/toolkit/components/antitracking/test/browser/browser_socialtracking_save_image.js
+++ b/toolkit/components/antitracking/test/browser/browser_socialtracking_save_image.js
@@ -48,7 +48,7 @@ function createPromiseForTransferComplete() {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   info("Setting up the prefs.");
 
   await SpecialPowers.pushPrefEnv({
diff --git a/toolkit/components/antitracking/test/browser/browser_staticPartition_saveAs.js b/toolkit/components/antitracking/test/browser/browser_staticPartition_saveAs.js
index d62bba9876eb1..c446ed2a37ac1 100644
--- a/toolkit/components/antitracking/test/browser/browser_staticPartition_saveAs.js
+++ b/toolkit/components/antitracking/test/browser/browser_staticPartition_saveAs.js
@@ -83,7 +83,7 @@ function createPromiseForObservingChannel(aURL, aPartitionKey) {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   info("Setting MockFilePicker.");
   mockTransferRegisterer.register();
 
diff --git a/toolkit/components/antitracking/test/browser/browser_staticPartition_websocket.js b/toolkit/components/antitracking/test/browser/browser_staticPartition_websocket.js
index bc8071df5a95a..19f4a85f8eb9f 100644
--- a/toolkit/components/antitracking/test/browser/browser_staticPartition_websocket.js
+++ b/toolkit/components/antitracking/test/browser/browser_staticPartition_websocket.js
@@ -188,7 +188,7 @@ async function runTest(partitioned) {
   await SpecialPowers.popPrefEnv();
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // This test relies on a WS connection timeout > 6 seconds.
   await SpecialPowers.pushPrefEnv({
     set: [["network.websocket.timeout.open", 20]],
diff --git a/toolkit/components/antitracking/test/browser/browser_storageAccessPrivilegeAPI.js b/toolkit/components/antitracking/test/browser/browser_storageAccessPrivilegeAPI.js
index 59d10ce6cca85..b402fb670f27e 100644
--- a/toolkit/components/antitracking/test/browser/browser_storageAccessPrivilegeAPI.js
+++ b/toolkit/components/antitracking/test/browser/browser_storageAccessPrivilegeAPI.js
@@ -93,7 +93,7 @@ function triggerSecondaryCommand() {
   triggerCommand("secondaryButton");
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["dom.storage_access.auto_grants", true],
diff --git a/toolkit/components/antitracking/test/browser/browser_storageAccessWithDynamicFpi.js b/toolkit/components/antitracking/test/browser/browser_storageAccessWithDynamicFpi.js
index c7735b9677095..3bb08117fe6e2 100644
--- a/toolkit/components/antitracking/test/browser/browser_storageAccessWithDynamicFpi.js
+++ b/toolkit/components/antitracking/test/browser/browser_storageAccessWithDynamicFpi.js
@@ -35,7 +35,7 @@ async function cleanup() {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.flushPrefEnv();
   await SpecialPowers.pushPrefEnv({
     set: [
diff --git a/toolkit/components/antitracking/test/browser/browser_storageAccessWithHeuristics.js b/toolkit/components/antitracking/test/browser/browser_storageAccessWithHeuristics.js
index cbad62200f9f8..9aafc342bb251 100644
--- a/toolkit/components/antitracking/test/browser/browser_storageAccessWithHeuristics.js
+++ b/toolkit/components/antitracking/test/browser/browser_storageAccessWithHeuristics.js
@@ -17,7 +17,7 @@ function waitStoragePermission() {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   info("Starting subResources test");
 
   await SpecialPowers.flushPrefEnv();
diff --git a/toolkit/components/antitracking/test/browser/browser_urlQueryStringStripping.js b/toolkit/components/antitracking/test/browser/browser_urlQueryStringStripping.js
index 90c24888c196a..ee23b29e7f35e 100644
--- a/toolkit/components/antitracking/test/browser/browser_urlQueryStringStripping.js
+++ b/toolkit/components/antitracking/test/browser/browser_urlQueryStringStripping.js
@@ -69,7 +69,7 @@ async function verifyQueryString(browser, expected) {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["privacy.query_stripping.strip_list", "paramToStrip1 paramToStrip2"],
diff --git a/toolkit/components/antitracking/test/browser/browser_urlQueryStringStripping_allowList.js b/toolkit/components/antitracking/test/browser/browser_urlQueryStringStripping_allowList.js
index d4869a6e0b023..37a4d9a26aad7 100644
--- a/toolkit/components/antitracking/test/browser/browser_urlQueryStringStripping_allowList.js
+++ b/toolkit/components/antitracking/test/browser/browser_urlQueryStringStripping_allowList.js
@@ -43,7 +43,7 @@ async function verifyQueryString(browser, expected) {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["privacy.query_stripping.strip_list", "paramToStrip"],
diff --git a/toolkit/components/antitracking/test/browser/browser_urlQueryStringStripping_telemetry.js b/toolkit/components/antitracking/test/browser/browser_urlQueryStringStripping_telemetry.js
index 5645c12c13a50..ab318846ce143 100644
--- a/toolkit/components/antitracking/test/browser/browser_urlQueryStringStripping_telemetry.js
+++ b/toolkit/components/antitracking/test/browser/browser_urlQueryStringStripping_telemetry.js
@@ -92,7 +92,7 @@ async function checkTelemetryProbe(probeInParent, expectedCnt, label) {
   is(cnt, expectedCnt, "There should be expected count in telemetry.");
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["privacy.query_stripping.enabled", true],
diff --git a/toolkit/components/cleardata/tests/browser/browser_image_cache.js b/toolkit/components/cleardata/tests/browser/browser_image_cache.js
index d51f2aa06bc46..28b84ba06962f 100644
--- a/toolkit/components/cleardata/tests/browser/browser_image_cache.js
+++ b/toolkit/components/cleardata/tests/browser/browser_image_cache.js
@@ -111,7 +111,7 @@ function cleanup() {
   imageCache.clearCache(true);
 }
 
-add_task(function setup() {
+add_setup(function() {
   cleanup();
 });
 
diff --git a/toolkit/components/cleardata/tests/browser/browser_quota.js b/toolkit/components/cleardata/tests/browser/browser_quota.js
index 2fe9a9615c8c1..13749410a8f2a 100644
--- a/toolkit/components/cleardata/tests/browser/browser_quota.js
+++ b/toolkit/components/cleardata/tests/browser/browser_quota.js
@@ -113,7 +113,7 @@ async function runTest(sites, deleteDataFunc) {
   }
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["dom.quotaManager.testing", true],
diff --git a/toolkit/components/cleardata/tests/browser/browser_serviceworkers.js b/toolkit/components/cleardata/tests/browser/browser_serviceworkers.js
index 61b375db878bf..e4d8cb63be3ed 100644
--- a/toolkit/components/cleardata/tests/browser/browser_serviceworkers.js
+++ b/toolkit/components/cleardata/tests/browser/browser_serviceworkers.js
@@ -19,7 +19,7 @@ async function addServiceWorker(origin) {
   ok(true, `${origin} has a service worker`);
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["dom.serviceWorkers.enabled", true],
diff --git a/toolkit/components/cleardata/tests/browser/browser_sessionStorage.js b/toolkit/components/cleardata/tests/browser/browser_sessionStorage.js
index b1144099f5cd3..733515cb3e86b 100644
--- a/toolkit/components/cleardata/tests/browser/browser_sessionStorage.js
+++ b/toolkit/components/cleardata/tests/browser/browser_sessionStorage.js
@@ -121,7 +121,7 @@ function cleanup() {
   Services.obs.notifyObservers(null, "browser:purge-sessionStorage");
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["network.cookie.cookieBehavior", 5]],
   });
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_autocomplete_popup.js b/toolkit/components/extensions/test/browser/browser_ext_themes_autocomplete_popup.js
index 73c8a03bdee7f..93eea45a37b99 100644
--- a/toolkit/components/extensions/test/browser/browser_ext_themes_autocomplete_popup.js
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_autocomplete_popup.js
@@ -21,7 +21,7 @@ XPCOMUtils.defineLazyModuleGetters(this, {
   UrlbarTestUtils: "resource://testing-common/UrlbarTestUtils.jsm",
 });
 
-add_task(async function setup() {
+add_setup(async function() {
   await PlacesUtils.history.clear();
   const NUM_VISITS = 10;
   let visits = [];
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_highlight.js b/toolkit/components/extensions/test/browser/browser_ext_themes_highlight.js
index 769232046d408..1325890e62595 100644
--- a/toolkit/components/extensions/test/browser/browser_ext_themes_highlight.js
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_highlight.js
@@ -6,7 +6,7 @@ const { CustomizableUITestUtils } = ChromeUtils.import(
   "resource://testing-common/CustomizableUITestUtils.jsm"
 );
 let gCUITestUtils = new CustomizableUITestUtils(window);
-add_task(async function setup() {
+add_setup(async function() {
   await gCUITestUtils.addSearchBar();
   await gFindBarPromise;
   registerCleanupFunction(() => {
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_pbm.js b/toolkit/components/extensions/test/browser/browser_ext_themes_pbm.js
index 93ff0a8182198..0f14d79cc0f3d 100644
--- a/toolkit/components/extensions/test/browser/browser_ext_themes_pbm.js
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_pbm.js
@@ -98,7 +98,7 @@ function getPrefersColorSchemeInfo({ win, chrome = false }) {
   return SpecialPowers.spawn(win.gBrowser.selectedBrowser, [], fn);
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // Set system theme to light to ensure consistency across test machines.
   await SpecialPowers.pushPrefEnv({
     set: [
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_toolbar_fields.js b/toolkit/components/extensions/test/browser/browser_ext_themes_toolbar_fields.js
index 7871659a474c0..74e0674245b48 100644
--- a/toolkit/components/extensions/test/browser/browser_ext_themes_toolbar_fields.js
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_toolbar_fields.js
@@ -8,7 +8,7 @@ const { CustomizableUITestUtils } = ChromeUtils.import(
 );
 let gCUITestUtils = new CustomizableUITestUtils(window);
 
-add_task(async function setup() {
+add_setup(async function() {
   await gCUITestUtils.addSearchBar();
   registerCleanupFunction(() => {
     gCUITestUtils.removeSearchBar();
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_toolbar_fields_focus.js b/toolkit/components/extensions/test/browser/browser_ext_themes_toolbar_fields_focus.js
index cf746cfb0abd7..b03dc043aa8cd 100644
--- a/toolkit/components/extensions/test/browser/browser_ext_themes_toolbar_fields_focus.js
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_toolbar_fields_focus.js
@@ -1,6 +1,6 @@
 "use strict";
 
-add_task(async function setup() {
+add_setup(async function() {
   // Remove the `remotecontrol` attribute since it interferes with the urlbar styling.
   document.documentElement.removeAttribute("remotecontrol");
   registerCleanupFunction(() => {
diff --git a/toolkit/components/extensions/test/browser/browser_ext_themes_warnings.js b/toolkit/components/extensions/test/browser/browser_ext_themes_warnings.js
index 64155006d9327..47f11445c53df 100644
--- a/toolkit/components/extensions/test/browser/browser_ext_themes_warnings.js
+++ b/toolkit/components/extensions/test/browser/browser_ext_themes_warnings.js
@@ -19,7 +19,7 @@ function waitForConsole(task, message) {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   SimpleTest.waitForExplicitFinish();
 });
 
diff --git a/toolkit/components/messaging-system/schemas/SpecialMessageActionSchemas/test/browser/browser_sma_configure_homepage.js b/toolkit/components/messaging-system/schemas/SpecialMessageActionSchemas/test/browser/browser_sma_configure_homepage.js
index 8bc734cece8a3..d998df1978a35 100644
--- a/toolkit/components/messaging-system/schemas/SpecialMessageActionSchemas/test/browser/browser_sma_configure_homepage.js
+++ b/toolkit/components/messaging-system/schemas/SpecialMessageActionSchemas/test/browser/browser_sma_configure_homepage.js
@@ -19,7 +19,7 @@ const SNIPPETS_PREF = "browser.newtabpage.activity-stream.feeds.snippets";
 const TOPSTORIES_PREF =
   "browser.newtabpage.activity-stream.feeds.system.topstories";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     // Highlights are preffed off by default.
     set: [[HIGHLIGHTS_PREF, true]],
diff --git a/toolkit/components/nimbus/test/browser/browser_nimbus_telemetry.js b/toolkit/components/nimbus/test/browser/browser_nimbus_telemetry.js
index f8dd52a19d1ce..23f527218a02d 100644
--- a/toolkit/components/nimbus/test/browser/browser_nimbus_telemetry.js
+++ b/toolkit/components/nimbus/test/browser/browser_nimbus_telemetry.js
@@ -20,7 +20,7 @@ const TELEMETRY_OBJECT = "nimbus_experiment";
 const EXPERIMENT_TYPE = "nimbus";
 const EVENT_FILTER = { category: TELEMETRY_CATEGORY };
 
-add_task(async function setup() {
+add_setup(async function() {
   let sandbox = sinon.createSandbox();
   // stub the `observe` method to make sure the Experiment Manager
   // pref listener doesn't trigger and cause side effects
diff --git a/toolkit/components/nimbus/test/browser/browser_remotesettings_experiment_enroll.js b/toolkit/components/nimbus/test/browser/browser_remotesettings_experiment_enroll.js
index 7734a036696e6..0681cf7f90cfd 100644
--- a/toolkit/components/nimbus/test/browser/browser_remotesettings_experiment_enroll.js
+++ b/toolkit/components/nimbus/test/browser/browser_remotesettings_experiment_enroll.js
@@ -18,7 +18,7 @@ const { ExperimentFakes } = ChromeUtils.import(
 
 let rsClient;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["messaging-system.log", "all"],
diff --git a/toolkit/components/nimbus/test/browser/browser_remotesettingsexperimentloader_force_enrollment.js b/toolkit/components/nimbus/test/browser/browser_remotesettingsexperimentloader_force_enrollment.js
index 36220919762c4..40fa7276364a0 100644
--- a/toolkit/components/nimbus/test/browser/browser_remotesettingsexperimentloader_force_enrollment.js
+++ b/toolkit/components/nimbus/test/browser/browser_remotesettingsexperimentloader_force_enrollment.js
@@ -37,7 +37,7 @@ async function setup(recipes) {
   return client;
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["messaging-system.log", "all"],
diff --git a/toolkit/components/nimbus/test/browser/head.js b/toolkit/components/nimbus/test/browser/head.js
index 3614aab9dc9e9..73c9f2f62a6a9 100644
--- a/toolkit/components/nimbus/test/browser/head.js
+++ b/toolkit/components/nimbus/test/browser/head.js
@@ -15,7 +15,7 @@ XPCOMUtils.defineLazyModuleGetters(this, {
   ExperimentFakes: "resource://testing-common/NimbusTestUtils.jsm",
 });
 
-add_task(function setup() {
+add_setup(function() {
   let sandbox = sinon.createSandbox();
 
   /* We stub the functions that operate with enrollments and remote rollouts
diff --git a/toolkit/components/normandy/test/browser/browser_Heartbeat.js b/toolkit/components/normandy/test/browser/browser_Heartbeat.js
index ef693daaf64a7..40ec98122d2e9 100644
--- a/toolkit/components/normandy/test/browser/browser_Heartbeat.js
+++ b/toolkit/components/normandy/test/browser/browser_Heartbeat.js
@@ -82,7 +82,7 @@ function getStars(notice) {
   return notice.buttonContainer.querySelectorAll(".star-x");
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   let win = await BrowserTestUtils.openNewBrowserWindow();
   // Open a new tab to keep the window open.
   await BrowserTestUtils.openNewForegroundTab(
diff --git a/toolkit/components/passwordmgr/test/browser/browser_autocomplete_autofocus_with_frame.js b/toolkit/components/passwordmgr/test/browser/browser_autocomplete_autofocus_with_frame.js
index b48057d7336a1..1a627cc3f6457 100644
--- a/toolkit/components/passwordmgr/test/browser/browser_autocomplete_autofocus_with_frame.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_autocomplete_autofocus_with_frame.js
@@ -1,6 +1,6 @@
 const TEST_URL_PATH = "https://example.org" + DIRECTORY_PATH;
 
-add_task(async function setup() {
+add_setup(async function() {
   let login = LoginTestUtils.testData.formLogin({
     origin: "https://example.org",
     formActionOrigin: "https://example.org",
diff --git a/toolkit/components/passwordmgr/test/browser/browser_autocomplete_generated_password_private_window.js b/toolkit/components/passwordmgr/test/browser/browser_autocomplete_generated_password_private_window.js
index 24832b13efcb2..29260f12df545 100644
--- a/toolkit/components/passwordmgr/test/browser/browser_autocomplete_generated_password_private_window.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_autocomplete_generated_password_private_window.js
@@ -4,7 +4,7 @@ const FORM_PAGE_PATH =
   "/browser/toolkit/components/passwordmgr/test/browser/form_basic.html";
 const passwordInputSelector = "#form-basic-password";
 
-add_task(async function setup() {
+add_setup(async function() {
   Services.telemetry.clearEvents();
   TelemetryTestUtils.assertEvents([], {
     category: "pwmgr",
diff --git a/toolkit/components/passwordmgr/test/browser/browser_autocomplete_primary_password.js b/toolkit/components/passwordmgr/test/browser/browser_autocomplete_primary_password.js
index 9ccd1f3c322d0..0c485c4c91ab5 100644
--- a/toolkit/components/passwordmgr/test/browser/browser_autocomplete_primary_password.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_autocomplete_primary_password.js
@@ -23,7 +23,7 @@ async function waitForDialog() {
   };
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   let login = LoginTestUtils.testData.formLogin({
     origin: "https://example.com",
     formActionOrigin: "https://example.com",
diff --git a/toolkit/components/passwordmgr/test/browser/browser_autofill_hidden_document.js b/toolkit/components/passwordmgr/test/browser/browser_autofill_hidden_document.js
index 2df2b2bd3902f..4695c4ba7ddd1 100644
--- a/toolkit/components/passwordmgr/test/browser/browser_autofill_hidden_document.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_autofill_hidden_document.js
@@ -48,7 +48,7 @@ function observePrimaryPasswordDialog(window, result) {
     });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   Services.prefs.setBoolPref("signon.usernameOnlyForm.enabled", true);
   registerCleanupFunction(() => {
     Services.prefs.clearUserPref("signon.usernameOnlyForm.enabled");
diff --git a/toolkit/components/passwordmgr/test/browser/browser_autofill_http.js b/toolkit/components/passwordmgr/test/browser/browser_autofill_http.js
index 9d457fcb76c24..df89b1f8d4e4e 100644
--- a/toolkit/components/passwordmgr/test/browser/browser_autofill_http.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_autofill_http.js
@@ -1,7 +1,7 @@
 const TEST_URL_PATH =
   "://example.org/browser/toolkit/components/passwordmgr/test/browser/";
 
-add_task(async function setup() {
+add_setup(async function() {
   let login = LoginTestUtils.testData.formLogin({
     origin: "http://example.org",
     formActionOrigin: "http://example.org",
diff --git a/toolkit/components/passwordmgr/test/browser/browser_basicAuth_multiTab.js b/toolkit/components/passwordmgr/test/browser/browser_basicAuth_multiTab.js
index 850aefc67bccd..732dca556df85 100644
--- a/toolkit/components/passwordmgr/test/browser/browser_basicAuth_multiTab.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_basicAuth_multiTab.js
@@ -80,7 +80,7 @@ async function testTabAuthed(expectAuthed, { tab, loadPromise, authOptions }) {
   is(pass, expectAuthed ? authOptions.pass : "", "Sent correct password");
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     // This test relies on tab auth prompts.
     set: [["prompts.modalType.httpAuth", Services.prompt.MODAL_TYPE_TAB]],
diff --git a/toolkit/components/passwordmgr/test/browser/browser_context_menu_generated_password.js b/toolkit/components/passwordmgr/test/browser/browser_context_menu_generated_password.js
index 9cb25216d0ce2..9d5d72c0bba90 100644
--- a/toolkit/components/passwordmgr/test/browser/browser_context_menu_generated_password.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_context_menu_generated_password.js
@@ -18,7 +18,7 @@ registerCleanupFunction(async function cleanup_resetPrefs() {
   await SpecialPowers.popPrefEnv();
 });
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["signon.generation.available", true],
diff --git a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_empty_password.js b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_empty_password.js
index bf0dfcea20a4c..0f855662e89fc 100644
--- a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_empty_password.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_empty_password.js
@@ -1,4 +1,4 @@
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["signon.rememberSignons.visibilityToggle", true]],
   });
diff --git a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_generated_password.js b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_generated_password.js
index 5b5b9e01ee718..972dfdb0a2e14 100644
--- a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_generated_password.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_generated_password.js
@@ -279,7 +279,7 @@ async function submitForm(browser) {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["signon.generation.available", true],
diff --git a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_promptToChangePassword.js b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_promptToChangePassword.js
index 886f3ad9154b3..41fb32789de96 100644
--- a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_promptToChangePassword.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_promptToChangePassword.js
@@ -95,7 +95,7 @@ async function setupLogins(...logins) {
   return savedLogins;
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["signon.autofillForms", false]],
   });
diff --git a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_remembering.js b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_remembering.js
index 0c2d5efd0d066..d8d5abf8ac6c8 100644
--- a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_remembering.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_remembering.js
@@ -51,7 +51,7 @@ let login2B = new nsLoginInfo(
 
 requestLongerTimeout(2);
 
-add_task(async function setup() {
+add_setup(async function() {
   // Load recipes for this test.
   let recipeParent = await LoginManagerParent.recipeParentPromise;
   await recipeParent.load({
diff --git a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_submit_telemetry.js b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_submit_telemetry.js
index 96ed22d403048..2ab0ec3170185 100644
--- a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_submit_telemetry.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_submit_telemetry.js
@@ -2,7 +2,7 @@
  * Test that doorhanger submit telemetry is sent when the user saves/updates.
  */
 
-add_task(function setup() {
+add_setup(function() {
   // This test used to rely on the initial timer of
   // TestUtils.waitForCondition. See bug 1695395.
   // The test is perma-fail on Linux asan opt without this.
diff --git a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_target_blank.js b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_target_blank.js
index 2ed6a0233573a..74274d6e93471 100644
--- a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_target_blank.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_target_blank.js
@@ -2,7 +2,7 @@
  * Test capture popup notifications when the login form uses target="_blank"
  */
 
-add_task(async function setup() {
+add_setup(async function() {
   await SimpleTest.promiseFocus(window);
 });
 
diff --git a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_toggles.js b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_toggles.js
index dcd711c4927ed..5b97805b7f92b 100644
--- a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_toggles.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_toggles.js
@@ -5,7 +5,7 @@ const usernameInputSelector = "#form-basic-username";
 const FORM_URL =
   "https://example.com/browser/toolkit/components/passwordmgr/test/browser/form_basic.html";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["signon.rememberSignons.visibilityToggle", true]],
   });
diff --git a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_window_open.js b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_window_open.js
index 6abd2f69952e6..2005e79e348f5 100644
--- a/toolkit/components/passwordmgr/test/browser/browser_doorhanger_window_open.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_doorhanger_window_open.js
@@ -54,7 +54,7 @@ function withTestTabUntilStorageChange(aPageFile, aTaskFn) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SimpleTest.promiseFocus(window);
 });
 
diff --git a/toolkit/components/passwordmgr/test/browser/browser_entry_point_telemetry.js b/toolkit/components/passwordmgr/test/browser/browser_entry_point_telemetry.js
index c82673e013c33..8f79682be8839 100644
--- a/toolkit/components/passwordmgr/test/browser/browser_entry_point_telemetry.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_entry_point_telemetry.js
@@ -1,6 +1,6 @@
 const TEST_ORIGIN = "https://example.com";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["signon.rememberSignons.visibilityToggle", true]],
   });
diff --git a/toolkit/components/passwordmgr/test/browser/browser_focus_before_first_DOMContentLoaded.js b/toolkit/components/passwordmgr/test/browser/browser_focus_before_first_DOMContentLoaded.js
index 4451fb94062bf..c81dabbb76432 100644
--- a/toolkit/components/passwordmgr/test/browser/browser_focus_before_first_DOMContentLoaded.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_focus_before_first_DOMContentLoaded.js
@@ -5,7 +5,7 @@
 
 "use strict";
 
-add_task(function setup() {
+add_setup(function() {
   let nsLoginInfo = Components.Constructor(
     "@mozilla.org/login-manager/loginInfo;1",
     Ci.nsILoginInfo,
diff --git a/toolkit/components/passwordmgr/test/browser/browser_formless_submit_chrome.js b/toolkit/components/passwordmgr/test/browser/browser_formless_submit_chrome.js
index db86dddbd1fc5..1b83dc5aef53b 100644
--- a/toolkit/components/passwordmgr/test/browser/browser_formless_submit_chrome.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_formless_submit_chrome.js
@@ -45,7 +45,7 @@ function withTestPage(aTaskFn) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SimpleTest.promiseFocus(window);
 });
 
diff --git a/toolkit/components/passwordmgr/test/browser/browser_localip_frame.js b/toolkit/components/passwordmgr/test/browser/browser_localip_frame.js
index 37650a5dece78..5e4b9b26c3d12 100644
--- a/toolkit/components/passwordmgr/test/browser/browser_localip_frame.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_localip_frame.js
@@ -1,6 +1,6 @@
 "use strict";
 
-add_task(async function setup() {
+add_setup(async function() {
   let login = LoginTestUtils.testData.formLogin({
     origin: "http://10.0.0.0",
     formActionOrigin: "https://example.org",
diff --git a/toolkit/components/passwordmgr/test/browser/browser_proxyAuth_prompt.js b/toolkit/components/passwordmgr/test/browser/browser_proxyAuth_prompt.js
index 7734bfa16de52..e4233f0799e31 100644
--- a/toolkit/components/passwordmgr/test/browser/browser_proxyAuth_prompt.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_proxyAuth_prompt.js
@@ -59,7 +59,7 @@ function initProxy() {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     // This test relies on tab auth prompts.
     set: [["prompts.modalType.httpAuth", Services.prompt.MODAL_TYPE_TAB]],
diff --git a/toolkit/components/passwordmgr/test/browser/browser_username_only_form_telemetry.js b/toolkit/components/passwordmgr/test/browser/browser_username_only_form_telemetry.js
index 32ca5dcc70f30..73696f57e5b62 100644
--- a/toolkit/components/passwordmgr/test/browser/browser_username_only_form_telemetry.js
+++ b/toolkit/components/passwordmgr/test/browser/browser_username_only_form_telemetry.js
@@ -70,7 +70,7 @@ async function checkChildHistogram(id, index, expected) {
   is(histogram.values[index], expected);
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   SpecialPowers.pushPrefEnv({
     set: [
       ["signon.usernameOnlyForm.enabled", true],
diff --git a/toolkit/components/pdfjs/test/browser_pdfjs_download_button.js b/toolkit/components/pdfjs/test/browser_pdfjs_download_button.js
index 9711209bd88c3..44bb8068bfd6c 100644
--- a/toolkit/components/pdfjs/test/browser_pdfjs_download_button.js
+++ b/toolkit/components/pdfjs/test/browser_pdfjs_download_button.js
@@ -27,7 +27,7 @@ function createPromiseForFilePicker() {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   tempDir = createTemporarySaveDirectory();
   MockFilePicker.displayDirectory = tempDir;
 
diff --git a/toolkit/components/pdfjs/test/browser_pdfjs_saveas.js b/toolkit/components/pdfjs/test/browser_pdfjs_saveas.js
index 0df10a39c4779..a124b38bf611b 100644
--- a/toolkit/components/pdfjs/test/browser_pdfjs_saveas.js
+++ b/toolkit/components/pdfjs/test/browser_pdfjs_saveas.js
@@ -38,7 +38,7 @@ function createPromiseForTransferComplete(expectedFileName, destFile) {
 
 let tempDir = createTemporarySaveDirectory();
 
-add_task(async function setup() {
+add_setup(async function() {
   mockTransferRegisterer.register();
   registerCleanupFunction(function() {
     mockTransferRegisterer.unregister();
diff --git a/toolkit/components/places/tests/browser/browser_visituri_privatebrowsing_perwindowpb.js b/toolkit/components/places/tests/browser/browser_visituri_privatebrowsing_perwindowpb.js
index 24779bd606b91..3a9178e2c229d 100644
--- a/toolkit/components/places/tests/browser/browser_visituri_privatebrowsing_perwindowpb.js
+++ b/toolkit/components/places/tests/browser/browser_visituri_privatebrowsing_perwindowpb.js
@@ -10,7 +10,7 @@ const finalURL =
 var observer;
 var visitSavedPromise;
 
-add_task(async function setup() {
+add_setup(async function() {
   visitSavedPromise = new Promise(resolve => {
     observer = {
       observe(subject, topic, data) {
diff --git a/toolkit/components/tooltiptext/tests/browser_input_file_tooltips.js b/toolkit/components/tooltiptext/tests/browser_input_file_tooltips.js
index 55641850595db..6970cfe9824cf 100644
--- a/toolkit/components/tooltiptext/tests/browser_input_file_tooltips.js
+++ b/toolkit/components/tooltiptext/tests/browser_input_file_tooltips.js
@@ -1,7 +1,7 @@
 /* eslint-disable mozilla/no-arbitrary-setTimeout */
 
 let tempFile;
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({ set: [["ui.tooltipDelay", 0]] });
   tempFile = createTempFile();
   registerCleanupFunction(function() {
diff --git a/toolkit/components/tooltiptext/tests/browser_shadow_dom_tooltip.js b/toolkit/components/tooltiptext/tests/browser_shadow_dom_tooltip.js
index 1af5385a6b6f0..8f4ea2607ab31 100644
--- a/toolkit/components/tooltiptext/tests/browser_shadow_dom_tooltip.js
+++ b/toolkit/components/tooltiptext/tests/browser_shadow_dom_tooltip.js
@@ -1,6 +1,6 @@
 /* eslint-disable mozilla/no-arbitrary-setTimeout */
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({ set: [["ui.tooltipDelay", 0]] });
 });
 
diff --git a/toolkit/components/viewsource/test/browser/browser_open_docgroup.js b/toolkit/components/viewsource/test/browser/browser_open_docgroup.js
index 48a63c97199f6..f9d2490fea308 100644
--- a/toolkit/components/viewsource/test/browser/browser_open_docgroup.js
+++ b/toolkit/components/viewsource/test/browser/browser_open_docgroup.js
@@ -6,7 +6,7 @@
  * bug 1340719.
  */
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["extensions.throw_on_docgroup_mismatch.enabled", true]],
   });
diff --git a/toolkit/components/viewsource/test/browser/browser_viewsourceprefs.js b/toolkit/components/viewsource/test/browser/browser_viewsourceprefs.js
index 155883531958b..871aca8e42c79 100644
--- a/toolkit/components/viewsource/test/browser/browser_viewsourceprefs.js
+++ b/toolkit/components/viewsource/test/browser/browser_viewsourceprefs.js
@@ -5,7 +5,7 @@
 var plaintextURL = "data:text/plain,hello+world";
 var htmlURL = "about:mozilla";
 
-add_task(async function setup() {
+add_setup(async function() {
   registerCleanupFunction(function() {
     SpecialPowers.clearUserPref("view_source.tab_size");
     SpecialPowers.clearUserPref("view_source.wrap_long_lines");
diff --git a/toolkit/components/windowwatcher/test/browser_new_remote_window_flags.js b/toolkit/components/windowwatcher/test/browser_new_remote_window_flags.js
index e395cdbdbf6a3..1ee8aa9f076d3 100644
--- a/toolkit/components/windowwatcher/test/browser_new_remote_window_flags.js
+++ b/toolkit/components/windowwatcher/test/browser_new_remote_window_flags.js
@@ -9,7 +9,7 @@ const SCRIPT_PAGE = `data:text/html,<script>window.open("about:blank", "_blank")
 // This magic value of 2 means that by default, when content tries
 // to open a new window, it'll actually open in a new window instead
 // of a new tab.
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["browser.link.open_newwindow", 2]],
   });
diff --git a/toolkit/modules/tests/browser/browser_CreditCard.js b/toolkit/modules/tests/browser/browser_CreditCard.js
index 8ddb8f6996350..8a6f599cd2332 100644
--- a/toolkit/modules/tests/browser/browser_CreditCard.js
+++ b/toolkit/modules/tests/browser/browser_CreditCard.js
@@ -16,7 +16,7 @@ const { OSKeyStoreTestUtils } = ChromeUtils.import(
 let oldGetters = {};
 let gFakeLoggedIn = true;
 
-add_task(function setup() {
+add_setup(function() {
   OSKeyStoreTestUtils.setup();
   oldGetters.isLoggedIn = Object.getOwnPropertyDescriptor(
     OSKeyStore,
diff --git a/toolkit/modules/tests/browser/browser_FinderHighlighter.js b/toolkit/modules/tests/browser/browser_FinderHighlighter.js
index fdaede7733540..ab116c9be4266 100644
--- a/toolkit/modules/tests/browser/browser_FinderHighlighter.js
+++ b/toolkit/modules/tests/browser/browser_FinderHighlighter.js
@@ -5,7 +5,7 @@ const kIteratorTimeout = Services.prefs.getIntPref("findbar.iteratorTimeout");
 const kPrefHighlightAll = "findbar.highlightAll";
 const kPrefModalHighlight = "findbar.modalHighlight";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       [kPrefHighlightAll, true],
diff --git a/toolkit/modules/tests/browser/browser_FinderHighlighter2.js b/toolkit/modules/tests/browser/browser_FinderHighlighter2.js
index 7da6da1bc4d1a..bb58a20e9e9c1 100644
--- a/toolkit/modules/tests/browser/browser_FinderHighlighter2.js
+++ b/toolkit/modules/tests/browser/browser_FinderHighlighter2.js
@@ -3,7 +3,7 @@
 const kPrefHighlightAll = "findbar.highlightAll";
 const kPrefModalHighlight = "findbar.modalHighlight";
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       [kPrefHighlightAll, true],
diff --git a/toolkit/mozapps/extensions/test/browser/browser_addon_list_reordering.js b/toolkit/mozapps/extensions/test/browser/browser_addon_list_reordering.js
index 83b4b33be60c3..092e0e35a85e8 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_addon_list_reordering.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_addon_list_reordering.js
@@ -66,7 +66,7 @@ function waitForTransitionEnd(...els) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // Ensure prefers-reduced-motion isn't set. Some linux environments will have
   // this enabled by default.
   await SpecialPowers.pushPrefEnv({
diff --git a/toolkit/mozapps/extensions/test/browser/browser_disco_taar_telemetry.js b/toolkit/mozapps/extensions/test/browser/browser_disco_taar_telemetry.js
index f6d27aa562c97..c5a42d7ccf4a1 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_disco_taar_telemetry.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_disco_taar_telemetry.js
@@ -22,7 +22,7 @@ const DISCO_URL = `http://${AMO_TEST_HOST}/discoapi`;
 // used in this test, this is set in the `setup` test task below.
 let getAddonIdFromDiscoResult;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       // Enabling the Data Upload pref may upload data.
diff --git a/toolkit/mozapps/extensions/test/browser/browser_html_abuse_report.js b/toolkit/mozapps/extensions/test/browser/browser_html_abuse_report.js
index 640bbcf069fdf..3fc3e4b3a6a7d 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_html_abuse_report.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_html_abuse_report.js
@@ -5,7 +5,7 @@
 
 loadTestSubscript("head_abuse_report.js");
 
-add_task(async function setup() {
+add_setup(async function() {
   await AbuseReportTestUtils.setup();
 });
 
diff --git a/toolkit/mozapps/extensions/test/browser/browser_html_abuse_report_dialog.js b/toolkit/mozapps/extensions/test/browser/browser_html_abuse_report_dialog.js
index 33078f96b1d97..1ddc180470be8 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_html_abuse_report_dialog.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_html_abuse_report_dialog.js
@@ -5,7 +5,7 @@
 
 loadTestSubscript("head_abuse_report.js");
 
-add_task(async function setup() {
+add_setup(async function() {
   await AbuseReportTestUtils.setup();
 });
 
diff --git a/toolkit/mozapps/extensions/test/browser/browser_html_discover_view.js b/toolkit/mozapps/extensions/test/browser/browser_html_discover_view.js
index a442456a4d1e9..4a21b5812de1f 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_html_discover_view.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_html_discover_view.js
@@ -199,7 +199,7 @@ async function testAddonUninstall(card) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       [
diff --git a/toolkit/mozapps/extensions/test/browser/browser_html_discover_view_clientid.js b/toolkit/mozapps/extensions/test/browser/browser_html_discover_view_clientid.js
index 2d6acb56f8f85..cd84e06bfb427 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_html_discover_view_clientid.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_html_discover_view_clientid.js
@@ -39,7 +39,7 @@ function isNoticeVisible(win) {
   return message && message.offsetHeight > 0;
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       // Enable clientid - see Discovery.jsm for the first two prefs.
diff --git a/toolkit/mozapps/extensions/test/browser/browser_html_discover_view_prefs.js b/toolkit/mozapps/extensions/test/browser/browser_html_discover_view_prefs.js
index 26635ad8ab352..aa73f02b46362 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_html_discover_view_prefs.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_html_discover_view_prefs.js
@@ -52,7 +52,7 @@ async function checkIfDiscoverVisible(expectVisible) {
   await close_manager(managerWindow);
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["extensions.getAddons.discovery.api_url", TEST_API_URL],
diff --git a/toolkit/mozapps/extensions/test/browser/browser_html_list_view.js b/toolkit/mozapps/extensions/test/browser/browser_html_list_view.js
index b77403c333366..ef7fdc71e8df6 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_html_list_view.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_html_list_view.js
@@ -33,7 +33,7 @@ function waitForThemeChange(list) {
 
 let mockProvider;
 
-add_task(async function setup() {
+add_setup(async function() {
   mockProvider = new MockProvider();
   promptService = mockPromptService();
   Services.telemetry.clearEvents();
diff --git a/toolkit/mozapps/extensions/test/browser/browser_html_list_view_recommendations.js b/toolkit/mozapps/extensions/test/browser/browser_html_list_view_recommendations.js
index 4fdfaf56f1763..3cf20dc5f1efe 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_html_list_view_recommendations.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_html_list_view_recommendations.js
@@ -35,7 +35,7 @@ function mockResults() {
   };
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   let results = btoa(JSON.stringify(mockResults()));
   await SpecialPowers.pushPrefEnv({
     set: [
diff --git a/toolkit/mozapps/extensions/test/browser/browser_html_message_bar.js b/toolkit/mozapps/extensions/test/browser/browser_html_message_bar.js
index 512d6d4674be0..d54acd0b318fa 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_html_message_bar.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_html_message_bar.js
@@ -32,7 +32,7 @@ function createMessageBar(messageBarStack, { attrs, children, onclose } = {}) {
   return messageBar;
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   htmlAboutAddonsWindow = await loadInitialView("extension");
   registerCleanupFunction(() => closeView(htmlAboutAddonsWindow));
 });
diff --git a/toolkit/mozapps/extensions/test/browser/browser_html_pending_updates.js b/toolkit/mozapps/extensions/test/browser/browser_html_pending_updates.js
index 2bc516051840b..a65164cb0b524 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_html_pending_updates.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_html_pending_updates.js
@@ -12,7 +12,7 @@ const LOCALE_ADDON_ID = "postponed-langpack@mochi.test";
 
 let gProvider;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["extensions.checkUpdateSecurity", false]],
   });
diff --git a/toolkit/mozapps/extensions/test/browser/browser_html_recommendations.js b/toolkit/mozapps/extensions/test/browser/browser_html_recommendations.js
index f7654089d4f25..3603edc8a8c78 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_html_recommendations.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_html_recommendations.js
@@ -14,7 +14,7 @@ const SUPPORT_URL = "http://support.allizom.org/support-dummy/";
 const SUMO_URL = SUPPORT_URL + "add-on-badges";
 const SUPPORTED_BADGES = ["recommended", "line", "verified"];
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["app.support.baseURL", SUPPORT_URL]],
   });
diff --git a/toolkit/mozapps/extensions/test/browser/browser_html_scroll_restoration.js b/toolkit/mozapps/extensions/test/browser/browser_html_scroll_restoration.js
index 690738d85ed97..351bf3f63ea3c 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_html_scroll_restoration.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_html_scroll_restoration.js
@@ -36,7 +36,7 @@ server.registerPathHandler("/discoapi", (request, response) => {
   response.write(JSON.stringify(results));
 });
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["extensions.getAddons.discovery.api_url", TEST_API_URL]],
   });
diff --git a/toolkit/mozapps/extensions/test/browser/browser_html_updates.js b/toolkit/mozapps/extensions/test/browser/browser_html_updates.js
index 677401168d541..359f6310a1dc7 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_html_updates.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_html_updates.js
@@ -13,7 +13,7 @@ registerCleanupFunction(() => {
   AddonManager.autoUpdateDefault = initialAutoUpdate;
 });
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["extensions.checkUpdateSecurity", false]],
   });
diff --git a/toolkit/mozapps/extensions/test/browser/browser_html_warning_messages.js b/toolkit/mozapps/extensions/test/browser/browser_html_warning_messages.js
index d2405273c6a51..ab6f1bb1d8d57 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_html_warning_messages.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_html_warning_messages.js
@@ -16,7 +16,7 @@ const SUPPORT_URL = Services.urlFormatter.formatURL(
   Services.prefs.getStringPref("app.support.baseURL")
 );
 
-add_task(async function setup() {
+add_setup(async function() {
   gProvider = new MockProvider();
 });
 
diff --git a/toolkit/mozapps/extensions/test/browser/browser_installtrigger_install.js b/toolkit/mozapps/extensions/test/browser/browser_installtrigger_install.js
index 09b127c2af4b0..fcba232cf55eb 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_installtrigger_install.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_installtrigger_install.js
@@ -18,7 +18,7 @@ AddonTestUtils.initMochitest(this);
 
 AddonTestUtils.hookAMTelemetryEvents();
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["extensions.webapi.testing", true],
diff --git a/toolkit/mozapps/extensions/test/browser/browser_interaction_telemetry.js b/toolkit/mozapps/extensions/test/browser/browser_interaction_telemetry.js
index 11f1c3b9070bf..7f79781ca2c4c 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_interaction_telemetry.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_interaction_telemetry.js
@@ -132,7 +132,7 @@ async function init(startPage) {
 
 /* Test functions start here. */
 
-add_task(async function setup() {
+add_setup(async function() {
   // Clear out any telemetry data that existed before this file is run.
   Services.telemetry.clearEvents();
 });
diff --git a/toolkit/mozapps/extensions/test/browser/browser_reinstall.js b/toolkit/mozapps/extensions/test/browser/browser_reinstall.js
index 49c9392493ae9..b6fc57f40cbcc 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_reinstall.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_reinstall.js
@@ -239,7 +239,7 @@ async function test_upgrade_pending_uninstall_disabled_v1_to_v2() {
   is(get_list_item_count(), 0, "Should be no items in the list");
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   xpi1 = await AddonTestUtils.createTempWebExtensionFile({
     manifest: {
       version: "1.0",
diff --git a/toolkit/mozapps/extensions/test/browser/browser_sidebar_hidden_categories.js b/toolkit/mozapps/extensions/test/browser/browser_sidebar_hidden_categories.js
index 690e7b5325d8f..21c31a55b430b 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_sidebar_hidden_categories.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_sidebar_hidden_categories.js
@@ -48,7 +48,7 @@ async function checkCategory(win, category, { expectHidden, expectSelected }) {
   }
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   gProvider = new MockProvider();
 });
 
diff --git a/toolkit/mozapps/extensions/test/browser/browser_subframe_install.js b/toolkit/mozapps/extensions/test/browser/browser_subframe_install.js
index 895be8c753250..0ade96c054c07 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_subframe_install.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_subframe_install.js
@@ -11,7 +11,7 @@ const XPI_URL = `${SECURE_TESTROOT}../xpinstall/amosigned.xpi`;
 
 AddonTestUtils.initMochitest(this);
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["extensions.install.requireBuiltInCerts", false]],
   });
diff --git a/toolkit/mozapps/extensions/test/browser/browser_webapi.js b/toolkit/mozapps/extensions/test/browser/browser_webapi.js
index ee1ef189e03c9..8462d65df39fb 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_webapi.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_webapi.js
@@ -4,7 +4,7 @@
 
 const TESTPAGE = `${SECURE_TESTROOT}webapi_checkavailable.html`;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["extensions.webapi.testing", true]],
   });
diff --git a/toolkit/mozapps/extensions/test/browser/browser_webapi_abuse_report.js b/toolkit/mozapps/extensions/test/browser/browser_webapi_abuse_report.js
index 3ec5650dae702..84178e27853f6 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_webapi_abuse_report.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_webapi_abuse_report.js
@@ -60,7 +60,7 @@ async function assertSubmittedReport(expectedReportProps) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await AbuseReportTestUtils.setup();
 
   await SpecialPowers.pushPrefEnv({
diff --git a/toolkit/mozapps/extensions/test/browser/browser_webapi_addon_listener.js b/toolkit/mozapps/extensions/test/browser/browser_webapi_addon_listener.js
index 996224a7f67a3..3264acc835d10 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_webapi_addon_listener.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_webapi_addon_listener.js
@@ -1,6 +1,6 @@
 const TESTPAGE = `${SECURE_TESTROOT}webapi_addon_listener.html`;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["extensions.webapi.testing", true]],
   });
diff --git a/toolkit/mozapps/extensions/test/browser/browser_webapi_enable.js b/toolkit/mozapps/extensions/test/browser/browser_webapi_enable.js
index 0bfbe198cd942..a69e131a8fc35 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_webapi_enable.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_webapi_enable.js
@@ -1,6 +1,6 @@
 const TESTPAGE = `${SECURE_TESTROOT}webapi_addon_listener.html`;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["extensions.webapi.testing", true]],
   });
diff --git a/toolkit/mozapps/extensions/test/browser/browser_webapi_install.js b/toolkit/mozapps/extensions/test/browser/browser_webapi_install.js
index ac32b43c66fd4..be074f43a4ec6 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_webapi_install.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_webapi_install.js
@@ -42,7 +42,7 @@ function waitForClear() {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["extensions.webapi.testing", true],
diff --git a/toolkit/mozapps/extensions/test/browser/browser_webapi_install_disabled.js b/toolkit/mozapps/extensions/test/browser/browser_webapi_install_disabled.js
index 32c94d3cc3234..c8ea0c2bd0ff0 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_webapi_install_disabled.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_webapi_install_disabled.js
@@ -17,7 +17,7 @@ function waitForClear() {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["extensions.webapi.testing", true],
diff --git a/toolkit/mozapps/extensions/test/browser/browser_webapi_uninstall.js b/toolkit/mozapps/extensions/test/browser/browser_webapi_uninstall.js
index 887c30ead36b0..3e8e16aa16607 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_webapi_uninstall.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_webapi_uninstall.js
@@ -4,7 +4,7 @@
 
 const TESTPAGE = `${SECURE_TESTROOT}webapi_checkavailable.html`;
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["extensions.webapi.testing", true]],
   });
diff --git a/uriloader/exthandler/tests/mochitest/browser_auto_close_window.js b/uriloader/exthandler/tests/mochitest/browser_auto_close_window.js
index e8a9bb9b63ec4..c70b62b3c3297 100644
--- a/uriloader/exthandler/tests/mochitest/browser_auto_close_window.js
+++ b/uriloader/exthandler/tests/mochitest/browser_auto_close_window.js
@@ -44,7 +44,7 @@ function promiseHelperAppDialog() {
 
 let mockHelperAppService;
 
-add_task(async function setup() {
+add_setup(async function() {
   // Replace the real helper app dialog with our own.
   mockHelperAppService = ComponentUtils._getFactory(HelperAppLauncherDialog);
   registrar.registerFactory(
diff --git a/uriloader/exthandler/tests/mochitest/browser_auto_close_window_nodialog.js b/uriloader/exthandler/tests/mochitest/browser_auto_close_window_nodialog.js
index 0243e2f83b1b8..900acc0b9e47b 100644
--- a/uriloader/exthandler/tests/mochitest/browser_auto_close_window_nodialog.js
+++ b/uriloader/exthandler/tests/mochitest/browser_auto_close_window_nodialog.js
@@ -50,7 +50,7 @@ function promiseSave() {
 
 let mockHelperAppService;
 
-add_task(async function setup() {
+add_setup(async function() {
   // Replace the real helper app dialog with our own.
   mockHelperAppService = ComponentUtils._getFactory(HelperAppLauncherDialog);
   registrar.registerFactory(
diff --git a/uriloader/exthandler/tests/mochitest/browser_download_open_with_internal_handler.js b/uriloader/exthandler/tests/mochitest/browser_download_open_with_internal_handler.js
index 03b7a97c1d4da..183f5691206fb 100644
--- a/uriloader/exthandler/tests/mochitest/browser_download_open_with_internal_handler.js
+++ b/uriloader/exthandler/tests/mochitest/browser_download_open_with_internal_handler.js
@@ -95,7 +95,7 @@ function checkTelemetry(desc, expectedAction, expectedType, expectedReason) {
   is(event[5].reason, expectedReason, desc + " telemetry reason");
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // Remove the security delay for the dialog during the test.
   await SpecialPowers.pushPrefEnv({
     set: [
diff --git a/uriloader/exthandler/tests/mochitest/browser_download_spam_permissions.js b/uriloader/exthandler/tests/mochitest/browser_download_spam_permissions.js
index b168375af28ac..e15340e21ed3f 100644
--- a/uriloader/exthandler/tests/mochitest/browser_download_spam_permissions.js
+++ b/uriloader/exthandler/tests/mochitest/browser_download_spam_permissions.js
@@ -23,7 +23,7 @@ registerCleanupFunction(() => MockFilePicker.cleanup());
 
 let gTempDownloadDir;
 
-add_task(async function setup() {
+add_setup(async function() {
   // Create temp directory
   let time = new Date().getTime();
   let tempDir = Services.dirsvc.get("TmpD", Ci.nsIFile);
diff --git a/uriloader/exthandler/tests/mochitest/browser_extension_correction.js b/uriloader/exthandler/tests/mochitest/browser_extension_correction.js
index d42f5ded37da0..912bc5e32beb1 100644
--- a/uriloader/exthandler/tests/mochitest/browser_extension_correction.js
+++ b/uriloader/exthandler/tests/mochitest/browser_extension_correction.js
@@ -10,7 +10,7 @@ const TEST_PATH = getRootDirectory(gTestPath).replace(
 
 let gPathsToRemove = [];
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["browser.download.useDownloadDir", true]],
   });
diff --git a/uriloader/exthandler/tests/mochitest/browser_launched_app_save_directory.js b/uriloader/exthandler/tests/mochitest/browser_launched_app_save_directory.js
index daff8d4466a3f..47911fffce6b7 100644
--- a/uriloader/exthandler/tests/mochitest/browser_launched_app_save_directory.js
+++ b/uriloader/exthandler/tests/mochitest/browser_launched_app_save_directory.js
@@ -11,7 +11,7 @@ const TEST_PATH = getRootDirectory(gTestPath).replace(
   "https://example.com"
 );
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.download.improvements_to_download_panel", true],
diff --git a/uriloader/exthandler/tests/mochitest/browser_local_files_open_doesnt_duplicate.js b/uriloader/exthandler/tests/mochitest/browser_local_files_open_doesnt_duplicate.js
index 0b24934300136..d779227b534af 100644
--- a/uriloader/exthandler/tests/mochitest/browser_local_files_open_doesnt_duplicate.js
+++ b/uriloader/exthandler/tests/mochitest/browser_local_files_open_doesnt_duplicate.js
@@ -9,7 +9,7 @@ const handlerSvc = Cc["@mozilla.org/uriloader/handler-service;1"].getService(
 );
 let mimeInfo = mimeSvc.getFromTypeAndExtension("application/pdf", "pdf");
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({ set: [["pdfjs.disabled", true]] });
 
   let oldAsk = mimeInfo.alwaysAskBeforeHandling;
diff --git a/uriloader/exthandler/tests/mochitest/browser_open_internal_choice_persistence.js b/uriloader/exthandler/tests/mochitest/browser_open_internal_choice_persistence.js
index 56862ed50ee2a..6b1dd5d054ef5 100644
--- a/uriloader/exthandler/tests/mochitest/browser_open_internal_choice_persistence.js
+++ b/uriloader/exthandler/tests/mochitest/browser_open_internal_choice_persistence.js
@@ -32,7 +32,7 @@ function waitForAcceptButtonToGetEnabled(doc) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   // Remove the security delay for the dialog during the test.
   await SpecialPowers.pushPrefEnv({
     set: [
diff --git a/uriloader/exthandler/tests/mochitest/browser_pdf_save_as.js b/uriloader/exthandler/tests/mochitest/browser_pdf_save_as.js
index 67cc685e1faa0..e3beb58d435e8 100644
--- a/uriloader/exthandler/tests/mochitest/browser_pdf_save_as.js
+++ b/uriloader/exthandler/tests/mochitest/browser_pdf_save_as.js
@@ -61,7 +61,7 @@ async function testPdfFilePicker(mimeInfo) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.download.improvements_to_download_panel", true],
diff --git a/uriloader/exthandler/tests/mochitest/browser_protocol_ask_dialog_external.js b/uriloader/exthandler/tests/mochitest/browser_protocol_ask_dialog_external.js
index 3a8661ab44c50..d937cf0d5e633 100644
--- a/uriloader/exthandler/tests/mochitest/browser_protocol_ask_dialog_external.js
+++ b/uriloader/exthandler/tests/mochitest/browser_protocol_ask_dialog_external.js
@@ -59,7 +59,7 @@ function makeCmdLineHelper(url) {
   );
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["network.protocol-handler.prompt-from-external", true]],
   });
diff --git a/uriloader/exthandler/tests/mochitest/browser_protocol_ask_dialog_permission.js b/uriloader/exthandler/tests/mochitest/browser_protocol_ask_dialog_permission.js
index b8a115c0c7295..a48cacb9e2810 100644
--- a/uriloader/exthandler/tests/mochitest/browser_protocol_ask_dialog_permission.js
+++ b/uriloader/exthandler/tests/mochitest/browser_protocol_ask_dialog_permission.js
@@ -555,7 +555,7 @@ registerCleanupFunction(function() {
   Services.perms.removeAll();
 });
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [["security.external_protocol_requires_permission", true]],
   });
diff --git a/uriloader/exthandler/tests/mochitest/browser_shows_where_to_save_dialog.js b/uriloader/exthandler/tests/mochitest/browser_shows_where_to_save_dialog.js
index 04ee0e8c7294a..447f7a1dcc2b1 100644
--- a/uriloader/exthandler/tests/mochitest/browser_shows_where_to_save_dialog.js
+++ b/uriloader/exthandler/tests/mochitest/browser_shows_where_to_save_dialog.js
@@ -22,7 +22,7 @@ const {
 let MockFilePicker = SpecialPowers.MockFilePicker;
 MockFilePicker.init(window);
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.download.improvements_to_download_panel", true],
diff --git a/uriloader/exthandler/tests/mochitest/browser_txt_download_save_as.js b/uriloader/exthandler/tests/mochitest/browser_txt_download_save_as.js
index 8ab7ecf99dd49..729c232bc34cb 100644
--- a/uriloader/exthandler/tests/mochitest/browser_txt_download_save_as.js
+++ b/uriloader/exthandler/tests/mochitest/browser_txt_download_save_as.js
@@ -86,7 +86,7 @@ async function setupFilePicker() {
   });
 }
 
-add_task(async function setup() {
+add_setup(async function() {
   await SpecialPowers.pushPrefEnv({
     set: [
       ["browser.download.improvements_to_download_panel", true],