diff --git a/tests/assertions.js b/tests/assertions.js
index da6f0c5c8..56459f2c5 100644
--- a/tests/assertions.js
+++ b/tests/assertions.js
@@ -1,4 +1,8 @@
-// some useful assertions for noVNC
+// Assertions that make it easier to use sinon
+import sinonChai from '../node_modules/sinon-chai/lib/sinon-chai.js';
+chai.use(sinonChai);
+
+// noVNC specific assertions
 chai.use(function (_chai, utils) {
     _chai.Assertion.addMethod('displayed', function (target_data) {
         var obj = this._obj;
diff --git a/tests/karma-test-main.js b/tests/karma-test-main.js
index fa7b78316..657e3121c 100644
--- a/tests/karma-test-main.js
+++ b/tests/karma-test-main.js
@@ -1,5 +1,6 @@
 var TEST_REGEXP = /test\..*\.js/;
 var allTestFiles = [];
+var extraFiles = ['/base/tests/assertions.js'];
 
 Object.keys(window.__karma__.files).forEach(function (file) {
     if (TEST_REGEXP.test(file)) {
@@ -10,6 +11,6 @@ Object.keys(window.__karma__.files).forEach(function (file) {
 
 require.config({
     baseUrl: '/base',
-    deps: allTestFiles,
+    deps: allTestFiles.concat(extraFiles),
     callback: window.__karma__.start,
 });
diff --git a/tests/test.display.js b/tests/test.display.js
index 9422c7cc5..fac0febc4 100644
--- a/tests/test.display.js
+++ b/tests/test.display.js
@@ -5,10 +5,7 @@ import Base64 from '../core/base64.js';
 import Display from '../core/display.js';
 import { _forceCursorURIs, browserSupportsCursorURIs } from '../core/util/browsers.js';
 
-import './assertions.js';
 import sinon from '../vendor/sinon.js';
-import sinonChai from '../node_modules/sinon-chai/lib/sinon-chai.js';
-chai.use(sinonChai);
 
 describe('Display/Canvas Helper', function () {
     var checked_data = [
diff --git a/tests/test.rfb.js b/tests/test.rfb.js
index d68b94232..fb6717730 100644
--- a/tests/test.rfb.js
+++ b/tests/test.rfb.js
@@ -6,10 +6,7 @@ import RFB from '../core/rfb.js';
 import Websock from '../core/websock.js';
 
 import FakeWebSocket from './fake.websocket.js';
-import './assertions';
 import sinon from '../vendor/sinon.js';
-import sinonChai from '../node_modules/sinon-chai/lib/sinon-chai.js';
-chai.use(sinonChai);
 
 function make_rfb (extra_opts) {
     if (!extra_opts) {
diff --git a/tests/test.util.js b/tests/test.util.js
index 3560675de..4ab2944f6 100644
--- a/tests/test.util.js
+++ b/tests/test.util.js
@@ -7,8 +7,6 @@ import * as Log from '../core/util/logging.js';
 import l10nGet, { l10n } from '../core/util/localization.js';
 
 import sinon from '../vendor/sinon.js';
-import sinonChai from '../node_modules/sinon-chai/lib/sinon-chai.js';
-chai.use(sinonChai);
 
 describe('Utils', function() {
     "use strict";
diff --git a/tests/test.websock.js b/tests/test.websock.js
index 499bcba22..f520ce9c9 100644
--- a/tests/test.websock.js
+++ b/tests/test.websock.js
@@ -5,10 +5,7 @@ var expect = chai.expect;
 import Websock from '../core/websock.js';
 import FakeWebSocket from './fake.websocket.js';
 
-import './assertions';
 import sinon from '../vendor/sinon.js';
-import sinonChai from '../node_modules/sinon-chai/lib/sinon-chai.js';
-chai.use(sinonChai);
 
 describe('Websock', function() {
     "use strict";