diff --git a/pipeline/aggregate/Blocks.ts b/pipeline/aggregate/Blocks.ts
index 4b8c4bed..7c7d34db 100644
--- a/pipeline/aggregate/Blocks.ts
+++ b/pipeline/aggregate/Blocks.ts
@@ -7,10 +7,10 @@ import ExternalStats from "@pipeline/aggregate/blocks/ExternalStats";
 import Growth from "@pipeline/aggregate/blocks/Growth";
 import InteractionStats from "@pipeline/aggregate/blocks/InteractionStats";
 import LanguageStats from "@pipeline/aggregate/blocks/LanguageStats";
-import MessagesPerCycle from "@pipeline/aggregate/blocks/MessagesPerCycle";
 import MessagesStats from "@pipeline/aggregate/blocks/MessagesStats";
 import SentimentPerCycle from "@pipeline/aggregate/blocks/SentimentPerCycle";
 import SentimentStats from "@pipeline/aggregate/blocks/SentimentStats";
+import MessagesPerCycle from "@pipeline/aggregate/blocks/messages/MessagesPerCycle";
 import { Database } from "@pipeline/process/Types";
 
 import WordStats from "./blocks/WordStats";
diff --git a/pipeline/aggregate/blocks/MessagesPerCycle.ts b/pipeline/aggregate/blocks/messages/MessagesPerCycle.ts
similarity index 93%
rename from pipeline/aggregate/blocks/MessagesPerCycle.ts
rename to pipeline/aggregate/blocks/messages/MessagesPerCycle.ts
index d4d890f1..fac29eff 100644
--- a/pipeline/aggregate/blocks/MessagesPerCycle.ts
+++ b/pipeline/aggregate/blocks/messages/MessagesPerCycle.ts
@@ -8,13 +8,17 @@ type MessagesInDate = {
     m: number; // messages
 };
 
+/**
+ * Number of messages per different time cycles.
+ * It ignores the time filter completely, all cycles are included.
+ */
 export interface MessagesPerCycle {
     perDay: MessagesInDate[];
     perWeek: MessagesInDate[];
     perMonth: MessagesInDate[];
 }
 
-const fn: BlockFn<MessagesPerCycle> = (database, filters, common, args) => {
+const fn: BlockFn<MessagesPerCycle> = (database, filters, common) => {
     const res: MessagesPerCycle = {
         perDay: [],
         perWeek: [],
diff --git a/report/components/viz/MessagesOverTime.tsx b/report/components/viz/MessagesOverTime.tsx
index 137e6290..0efa6600 100644
--- a/report/components/viz/MessagesOverTime.tsx
+++ b/report/components/viz/MessagesOverTime.tsx
@@ -14,7 +14,7 @@ import {
     XYSeries,
 } from "@amcharts/amcharts5/xy";
 import { Filter } from "@pipeline/aggregate/Blocks";
-import { MessagesPerCycle } from "@pipeline/aggregate/blocks/MessagesPerCycle";
+import { MessagesPerCycle } from "@pipeline/aggregate/blocks/messages/MessagesPerCycle";
 import { getWorker } from "@report/WorkerWrapper";
 
 import { Themes } from "./AmCharts5";
diff --git a/tests/aggregate/Common.ts b/tests/aggregate/Common.ts
new file mode 100644
index 00000000..33439ab6
--- /dev/null
+++ b/tests/aggregate/Common.ts
@@ -0,0 +1,13 @@
+import { generateDatabase } from "@pipeline/index";
+
+import { TestEnv, loadSamples } from "@tests/samples";
+
+export const loadTestDatabase = async () => {
+    const samples = await loadSamples(["discord/GC_3A_5M.json", "discord/SV_5A_5M.json"]);
+    const db = await generateDatabase(
+        samples.map((s) => s.input),
+        { platform: "discord" },
+        TestEnv
+    );
+    return db;
+};
diff --git a/tests/aggregate/Helper.test.ts b/tests/aggregate/Helper.test.ts
new file mode 100644
index 00000000..38a7f9b6
--- /dev/null
+++ b/tests/aggregate/Helper.test.ts
@@ -0,0 +1,83 @@
+import { Index } from "@pipeline/Types";
+import { computeCommonBlockData } from "@pipeline/aggregate/Common";
+import { Filters } from "@pipeline/aggregate/Filters";
+import { filterMessages } from "@pipeline/aggregate/Helpers";
+import { Database, Message } from "@pipeline/process/Types";
+import { BitStream } from "@pipeline/serialization/BitStream";
+import { MessagesArray } from "@pipeline/serialization/MessagesArray";
+
+import { loadTestDatabase } from "@tests/aggregate/Common";
+
+let db: Database;
+let fn: jest.Mock;
+let filters: Filters;
+
+let allowedAuthors: Index[];
+let allowedChannels: Index[];
+let allowedDays: Index[];
+
+let allMessages: { msg: Message; channelIndex: Index }[];
+
+beforeEach(async () => {
+    fn = jest.fn();
+    db = await loadTestDatabase();
+
+    allMessages = [];
+    for (const channel of db.channels) {
+        const channelIndex = db.channels.indexOf(channel);
+        const stream = new BitStream(db.messages.buffer);
+        if (channel.msgAddr !== undefined) {
+            stream.offset = channel.msgAddr;
+            const arr = new MessagesArray(db.bitConfig, stream, channel.msgCount);
+            for (const msg of arr) {
+                allMessages.push({ msg, channelIndex });
+            }
+        }
+    }
+
+    const dateKeys = computeCommonBlockData(db).timeKeys.dateKeys;
+    allowedAuthors = db.authors.slice(0, db.authors.length / 2).map((_, i) => i);
+    allowedChannels = db.channels.slice(0, db.channels.length / 2).map((_, i) => i);
+    const days = dateKeys.slice(0, dateKeys.length / 2);
+    allowedDays = days.map((_, i) => i);
+
+    filters = new Filters(db);
+    filters.updateAuthors(allowedAuthors);
+    filters.updateChannels(allowedChannels);
+    filters.updateEndDate(days[days.length - 1]);
+});
+
+describe("filterMessages", () => {
+    // prettier-ignore
+    test.each([
+        { authors: false, channels: false, time: false, },
+        { authors: false, channels: false, time: true, },
+        { authors: false, channels: true, time: false, },
+        { authors: false, channels: true, time: true, },
+        { authors: true, channels: false, time: false, },
+        { authors: true, channels: false, time: true, },
+        { authors: true, channels: true, time: false, },
+        { authors: true, channels: true, time: true, },
+    ])(`filters with active %p`, (activeFilters) => {
+        filterMessages(fn, db, filters, activeFilters);
+
+        const expectedMessages = allMessages.filter(({channelIndex,msg}) => {
+            return (
+                (!activeFilters.authors || allowedAuthors.includes(msg.authorIndex)) &&
+                (!activeFilters.channels || allowedChannels.includes(channelIndex)) &&
+                (!activeFilters.time || allowedDays.includes(msg.dayIndex))
+            );
+        });
+
+        expect(fn).toHaveBeenCalledTimes(expectedMessages.length);
+
+        for (const { msg } of expectedMessages) {
+            expect(fn).toHaveBeenCalledWith(expect.objectContaining({
+                authorIndex: msg.authorIndex,
+                dayIndex: msg.dayIndex,
+                secondOfDay: msg.secondOfDay,
+                langIndex: msg.langIndex,
+            }));
+        }
+    });
+});
diff --git a/tests/aggregate/messages/MessagesPerCycle.test.ts b/tests/aggregate/messages/MessagesPerCycle.test.ts
new file mode 100644
index 00000000..ddfb30d8
--- /dev/null
+++ b/tests/aggregate/messages/MessagesPerCycle.test.ts
@@ -0,0 +1 @@
+test("MessagesPerCycle", async () => {});