Use vitest for some EW unit tests (#33816)

* Use vitest for some EW unit tests

* Ensure library builds are done before unit tests

* Stabilise jest tests

* Move more tests over

* Make sonar happier

* Update types/node for happy-dom compat again

* Decrease max-workers to stabilise jest tests

* Split jest over 3 runners to alleviate memory woes

* Switch jest to runInBand

* Attempt to deflake jest tests

* tweak coverage

* tweak coverage

apps/web/.eslintrc.cjs

@@ -232,7 +232,7 @@ module.exports = {
             },
         },
         {
-            files: ["test/**/*.{ts,tsx}", "playwright/**/*.ts"],
+            files: ["src/**/*.test.{ts,tsx}", "test/**/*.{ts,tsx}", "playwright/**/*.ts"],
             extends: ["plugin:matrix-org/jest"],
             rules: {
                 // We don't need super strict typing in test utilities

apps/web/jest.config.ts

@@ -52,16 +52,19 @@ const config: Config = {
     ],
     collectCoverageFrom: [
         "<rootDir>/src/**/*.{js,ts,tsx}",
-        "<rootDir>/packages/**/*.{js,ts,tsx}",
         // getSessionLock is piped into a different JS context via stringification, and the coverage functionality is
         // not available in that contest. So, turn off coverage instrumentation for it.
         "!<rootDir>/src/utils/SessionLock.ts",
         // Coverage chokes on type definition files
         "!<rootDir>/src/**/*.d.ts",
+        // Ignore vitest tests
+        "!<rootDir>/src/**/*.test.{ts,tsx}",
+        "!<rootDir>/src/test/**",
     ],
     coverageReporters: ["text-summary", ["lcov", { projectRoot: "../../" }]],
     prettierPath: null,
     moduleDirectories: ["node_modules", "test/test-utils"],
+    workerIdleMemoryLimit: "512MB",
 };
 
 // if we're running under GHA, enable relevant reporters

apps/web/package.json

@@ -30,6 +30,7 @@
         "lint:types": "nx lint:types",
         "lint:style": "stylelint \"res/css/**/*.pcss\"",
         "test": "nx test:unit",
+        "test:vitest": "nx test:vitest",
         "test:playwright": "nx test:playwright --",
         "test:playwright:open": "nx test:playwright -- --ui",
         "test:playwright:screenshots": "nx test:playwright:screenshots --",
@@ -129,6 +130,7 @@
         "@element-hq/element-call-embedded": "0.20.1",
         "@element-hq/element-web-playwright-common": "workspace:*",
         "@fetch-mock/jest": "^0.2.20",
+        "@fetch-mock/vitest": "^0.2.18",
         "@jest/globals": "^30.2.0",
         "@peculiar/webcrypto": "^1.4.3",
         "@playwright/test": "catalog:",
@@ -190,6 +192,7 @@
         "express": "^5.0.0",
         "fake-indexeddb": "^6.0.0",
         "file-loader": "^6.0.0",
+        "happy-dom": "^20.10.2",
         "html-webpack-plugin": "^5.5.3",
         "identity-obj-proxy": "^3.0.0",
         "jest": "^30.0.0",
@@ -226,6 +229,7 @@
         "testcontainers": "^12.0.0",
         "typescript": "catalog:",
         "util": "^0.12.5",
+        "vitest": "catalog:",
         "web-streams-polyfill": "^4.0.0",
         "webpack": "^5.89.0",
         "webpack-bundle-analyzer": "^5.0.0",

apps/web/project.json

@@ -46,11 +46,20 @@
             },
             "dependsOn": ["^build", "^build:playwright"]
         },
+        "test:unit:prepare": {
+            "executor": "nx:noop",
+            "dependsOn": ["^build"]
+        },
         "test:unit": {
             // We avoid the jest executor because it doesn't seem to give any benefit, and it mangles the summary of failing tests.
             "command": "jest",
             "options": { "cwd": "apps/web" },
-            "dependsOn": ["^build"]
+            "dependsOn": ["test:unit:prepare"]
+        },
+        "test:vitest": {
+            "command": "vitest run",
+            "options": { "cwd": "apps/web" },
+            "dependsOn": ["test:unit:prepare"]
         },
         "test:playwright": {
             "command": "playwright test",

apps/web/src/UserActivity.test.ts

@@ -5,9 +5,12 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
-import EventEmitter from "events";
+// @vitest-environment happy-dom
 
-import UserActivity from "../../src/UserActivity";
+import { vi, describe, it, expect, beforeEach, afterEach } from "vitest";
+import EventEmitter from "node:events";
+
+import UserActivity from "./UserActivity";
 
 class FakeDomEventEmitter extends EventEmitter {
     addEventListener(what: string, l: (...args: any[]) => void) {
@@ -29,7 +32,7 @@ describe("UserActivity", function () {
         fakeDocument = new FakeDomEventEmitter();
         userActivity = new UserActivity(fakeWindow as unknown as Window, fakeDocument as unknown as Document);
         userActivity.start();
-        jest.useFakeTimers();
+        vi.useFakeTimers();
     });
 
     afterEach(function () {
@@ -49,7 +52,7 @@ describe("UserActivity", function () {
     });
 
     it("should not consider user active after activity if no window focus", function () {
-        fakeDocument.hasFocus = jest.fn().mockReturnValue(false);
+        fakeDocument.hasFocus = vi.fn().mockReturnValue(false);
 
         userActivity.onUserActivity({ type: "event" } as Event);
         expect(userActivity.userActiveNow()).toBe(false);
@@ -57,62 +60,62 @@ describe("UserActivity", function () {
     });
 
     it("should consider user active shortly after activity", function () {
-        fakeDocument.hasFocus = jest.fn().mockReturnValue(true);
+        fakeDocument.hasFocus = vi.fn().mockReturnValue(true);
 
         userActivity.onUserActivity({ type: "event" } as Event);
         expect(userActivity.userActiveNow()).toBe(true);
         expect(userActivity.userActiveRecently()).toBe(true);
-        jest.advanceTimersByTime(200);
+        vi.advanceTimersByTime(200);
         expect(userActivity.userActiveNow()).toBe(true);
         expect(userActivity.userActiveRecently()).toBe(true);
     });
 
     it("should consider user not active after 10s of no activity", function () {
-        fakeDocument.hasFocus = jest.fn().mockReturnValue(true);
+        fakeDocument.hasFocus = vi.fn().mockReturnValue(true);
 
         userActivity.onUserActivity({ type: "event" } as Event);
-        jest.advanceTimersByTime(10000);
+        vi.advanceTimersByTime(10000);
         expect(userActivity.userActiveNow()).toBe(false);
     });
 
     it("should consider user passive after 10s of no activity", function () {
-        fakeDocument.hasFocus = jest.fn().mockReturnValue(true);
+        fakeDocument.hasFocus = vi.fn().mockReturnValue(true);
 
         userActivity.onUserActivity({ type: "event" } as Event);
-        jest.advanceTimersByTime(10000);
+        vi.advanceTimersByTime(10000);
         expect(userActivity.userActiveRecently()).toBe(true);
     });
 
     it("should not consider user passive after 10s if window un-focused", function () {
-        fakeDocument.hasFocus = jest.fn().mockReturnValue(true);
+        fakeDocument.hasFocus = vi.fn().mockReturnValue(true);
 
         userActivity.onUserActivity({ type: "event" } as Event);
-        jest.advanceTimersByTime(10000);
+        vi.advanceTimersByTime(10000);
 
-        fakeDocument.hasFocus = jest.fn().mockReturnValue(false);
+        fakeDocument.hasFocus = vi.fn().mockReturnValue(false);
         fakeWindow.emit("blur", {});
 
         expect(userActivity.userActiveRecently()).toBe(false);
     });
 
     it("should not consider user passive after 3 mins", function () {
-        fakeDocument.hasFocus = jest.fn().mockReturnValue(true);
+        fakeDocument.hasFocus = vi.fn().mockReturnValue(true);
 
         userActivity.onUserActivity({ type: "event" } as Event);
-        jest.advanceTimersByTime(3 * 60 * 1000);
+        vi.advanceTimersByTime(3 * 60 * 1000);
 
         expect(userActivity.userActiveRecently()).toBe(false);
     });
 
     it("should extend timer on activity", function () {
-        fakeDocument.hasFocus = jest.fn().mockReturnValue(true);
+        fakeDocument.hasFocus = vi.fn().mockReturnValue(true);
 
         userActivity.onUserActivity({ type: "event" } as Event);
-        jest.advanceTimersByTime(1 * 60 * 1000);
+        vi.advanceTimersByTime(1 * 60 * 1000);
         userActivity.onUserActivity({ type: "event" } as Event);
-        jest.advanceTimersByTime(1 * 60 * 1000);
+        vi.advanceTimersByTime(1 * 60 * 1000);
         userActivity.onUserActivity({ type: "event" } as Event);
-        jest.advanceTimersByTime(1 * 60 * 1000);
+        vi.advanceTimersByTime(1 * 60 * 1000);
 
         expect(userActivity.userActiveRecently()).toBe(true);
     });

apps/web/src/WorkerManager.test.ts

@@ -6,11 +6,13 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
-import { WorkerManager } from "../../src/WorkerManager";
+import { vi, describe, it, expect } from "vitest";
+
+import { WorkerManager } from "./WorkerManager";
 
 describe("WorkerManager", () => {
     it("should generate consecutive sequence numbers for each call", () => {
-        const postMessage = jest.fn();
+        const postMessage = vi.fn();
         const manager = new WorkerManager({ postMessage } as unknown as Worker);
 
         manager.call({ data: "One" });
@@ -27,7 +29,7 @@ describe("WorkerManager", () => {
     });
 
     it("should support resolving out of order", async () => {
-        const postMessage = jest.fn();
+        const postMessage = vi.fn();
         const worker = { postMessage } as unknown as Worker;
         const manager = new WorkerManager(worker);
 

apps/web/src/email.test.ts

@@ -6,7 +6,9 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
-import { looksValid } from "../../src/email";
+import { describe, it, expect } from "vitest";
+
+import { looksValid } from "./email";
 
 describe("looksValid", () => {
     it.each([

apps/web/src/test/setupTests.ts

@@ -0,0 +1,18 @@
+/*
+Copyright 2026 Element Creations Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE files in the repository root for full details.
+*/
+
+import { beforeEach } from "vitest";
+import fetchMock, { manageFetchMockGlobally } from "@fetch-mock/vitest";
+
+manageFetchMockGlobally();
+
+beforeEach(() => {
+    // set up fetch API mock
+    fetchMock.hardReset();
+    fetchMock.catch(404);
+    fetchMock.mockGlobal();
+});

apps/web/src/utils/AnimationUtils.test.ts

@@ -6,7 +6,9 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
-import { lerp } from "../../../src/utils/AnimationUtils";
+import { describe, it, expect } from "vitest";
+
+import { lerp } from "./AnimationUtils";
 
 describe("lerp", () => {
     it("correctly interpolates", () => {

apps/web/src/utils/FixedRollingArray.test.ts

@@ -6,7 +6,9 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
-import { FixedRollingArray } from "../../../src/utils/FixedRollingArray";
+import { describe, it, expect } from "vitest";
+
+import { FixedRollingArray } from "./FixedRollingArray";
 
 describe("FixedRollingArray", () => {
     it("should seed the array with the given value", () => {

apps/web/src/utils/Image.test.ts

@@ -6,10 +6,13 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
-import fs from "fs";
-import path from "path";
+import { describe, it, expect } from "vitest";
+import fs from "node:fs";
+import path from "node:path";
 
-import { blobIsAnimated, mayBeAnimated } from "../../src/utils/Image";
+import { blobIsAnimated, mayBeAnimated } from "./Image";
+
+const imagesDir = path.resolve(__dirname, "../../test/unit-tests/images");
 
 describe("Image", () => {
     describe("mayBeAnimated", () => {
@@ -32,28 +35,28 @@ describe("Image", () => {
 
     describe("blobIsAnimated", () => {
         it("Animated GIF", async () => {
-            const img = new Blob([fs.readFileSync(path.resolve(__dirname, "images", "animated-logo.gif")).slice()], {
+            const img = new Blob([fs.readFileSync(path.resolve(imagesDir, "animated-logo.gif")).slice()], {
                 type: "image/gif",
             });
             expect(await blobIsAnimated(img)).toBeTruthy();
         });
 
         it("Static GIF", async () => {
-            const img = new Blob([fs.readFileSync(path.resolve(__dirname, "images", "static-logo.gif")).slice()], {
+            const img = new Blob([fs.readFileSync(path.resolve(imagesDir, "static-logo.gif")).slice()], {
                 type: "image/gif",
             });
             expect(await blobIsAnimated(img)).toBeFalsy();
         });
 
         it("Animated WEBP", async () => {
-            const img = new Blob([fs.readFileSync(path.resolve(__dirname, "images", "animated-logo.webp")).slice()], {
+            const img = new Blob([fs.readFileSync(path.resolve(imagesDir, "animated-logo.webp")).slice()], {
                 type: "image/webp",
             });
             expect(await blobIsAnimated(img)).toBeTruthy();
         });
 
         it("Static WEBP", async () => {
-            const img = new Blob([fs.readFileSync(path.resolve(__dirname, "images", "static-logo.webp")).slice()], {
+            const img = new Blob([fs.readFileSync(path.resolve(imagesDir, "static-logo.webp")).slice()], {
                 type: "image/webp",
             });
             expect(await blobIsAnimated(img)).toBeFalsy();
@@ -61,14 +64,14 @@ describe("Image", () => {
 
         it("Static WEBP in extended file format", async () => {
             const img = new Blob(
-                [fs.readFileSync(path.resolve(__dirname, "images", "static-logo-extended-file-format.webp")).slice()],
+                [fs.readFileSync(path.resolve(imagesDir, "static-logo-extended-file-format.webp")).slice()],
                 { type: "image/webp" },
             );
             expect(await blobIsAnimated(img)).toBeFalsy();
         });
 
         it("Animated PNG", async () => {
-            const img = new Blob([fs.readFileSync(path.resolve(__dirname, "images", "animated-logo.apng")).slice()]);
+            const img = new Blob([fs.readFileSync(path.resolve(imagesDir, "animated-logo.apng")).slice()]);
             const pngBlob = img.slice(0, img.size, "image/png");
             const apngBlob = img.slice(0, img.size, "image/apng");
             expect(await blobIsAnimated(pngBlob)).toBeTruthy();
@@ -76,7 +79,7 @@ describe("Image", () => {
         });
 
         it("Static PNG", async () => {
-            const img = new Blob([fs.readFileSync(path.resolve(__dirname, "images", "static-logo.png")).slice()]);
+            const img = new Blob([fs.readFileSync(path.resolve(imagesDir, "static-logo.png")).slice()]);
             const pngBlob = img.slice(0, img.size, "image/png");
             const apngBlob = img.slice(0, img.size, "image/apng");
             expect(await blobIsAnimated(pngBlob)).toBeFalsy();

apps/web/src/utils/LruCache.test.ts

@@ -6,21 +6,18 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
+import { vi, describe, it, expect, beforeEach } from "vitest";
 import { logger } from "matrix-js-sdk/src/logger";
 
-import { LruCache } from "../../../src/utils/LruCache";
+import { LruCache } from "./LruCache";
 
 describe("LruCache", () => {
     it("when creating a cache with negative capacity it should raise an error", () => {
-        expect(() => {
-            new LruCache(-23);
-        }).toThrow("Cache capacity must be at least 1");
+        expect(() => new LruCache(-23)).toThrow("Cache capacity must be at least 1");
     });
 
     it("when creating a cache with 0 capacity it should raise an error", () => {
-        expect(() => {
-            new LruCache(0);
-        }).toThrow("Cache capacity must be at least 1");
+        expect(() => new LruCache(0)).toThrow("Cache capacity must be at least 1");
     });
 
     describe("when there is a cache with a capacity of 3", () => {
@@ -72,7 +69,7 @@ describe("LruCache", () => {
             });
 
             it("when an error occurs while setting an item the cache should be cleard", () => {
-                jest.spyOn(logger, "warn");
+                vi.spyOn(logger, "warn");
                 const err = new Error("Something weng wrong :(");
 
                 // @ts-ignore

apps/web/src/utils/PreferredRoomVersions.test.ts

@@ -6,7 +6,9 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
-import { doesRoomVersionSupport, PreferredRoomVersions } from "../../src/utils/PreferredRoomVersions";
+import { describe, it, expect } from "vitest";
+
+import { doesRoomVersionSupport, PreferredRoomVersions } from "./PreferredRoomVersions";
 
 describe("doesRoomVersionSupport", () => {
     it("should detect unstable as unsupported", () => {

apps/web/src/utils/SnakedObject.test.ts

@@ -6,7 +6,9 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
-import { SnakedObject, snakeToCamel } from "../../../src/utils/SnakedObject";
+import { describe, it, expect } from "vitest";
+
+import { SnakedObject, snakeToCamel } from "./SnakedObject";
 
 describe("snakeToCamel", () => {
     it("should convert snake_case to camelCase in simple scenarios", () => {

apps/web/src/utils/UrlUtils.test.ts

@@ -6,7 +6,11 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
-import { abbreviateUrl, parseUrl, unabbreviateUrl } from "../../../src/utils/UrlUtils";
+// @vitest-environment happy-dom
+
+import { describe, it, expect } from "vitest";
+
+import { abbreviateUrl, parseUrl, unabbreviateUrl } from "./UrlUtils";
 
 describe("abbreviateUrl", () => {
     it("should return empty string if passed falsey", () => {

apps/web/src/utils/arrays.test.ts

@@ -6,6 +6,8 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
+import { vi, describe, it, expect } from "vitest";
+
 import {
     arrayDiff,
     arrayFastClone,
@@ -25,7 +27,7 @@ import {
     asyncSome,
     asyncSomeParallel,
     asyncFilter,
-} from "../../../src/utils/arrays";
+} from "./arrays";
 
 type TestParams = { input: number[]; output: number[] };
 type TestCase = [string, TestParams];
@@ -412,11 +414,11 @@ describe("arrays", () => {
 
     describe("asyncEvery", () => {
         it("when called with an empty array, it should return true", async () => {
-            expect(await asyncEvery([], jest.fn().mockResolvedValue(true))).toBe(true);
+            expect(await asyncEvery([], vi.fn().mockResolvedValue(true))).toBe(true);
         });
 
         it("when called with some items and the predicate resolves to true for all of them, it should return true", async () => {
-            const predicate = jest.fn().mockResolvedValue(true);
+            const predicate = vi.fn().mockResolvedValue(true);
             expect(await asyncEvery([1, 2, 3], predicate)).toBe(true);
             expect(predicate).toHaveBeenCalledTimes(3);
             expect(predicate).toHaveBeenCalledWith(1);
@@ -425,14 +427,14 @@ describe("arrays", () => {
         });
 
         it("when called with some items and the predicate resolves to false for all of them, it should return false", async () => {
-            const predicate = jest.fn().mockResolvedValue(false);
+            const predicate = vi.fn().mockResolvedValue(false);
             expect(await asyncEvery([1, 2, 3], predicate)).toBe(false);
             expect(predicate).toHaveBeenCalledTimes(1);
             expect(predicate).toHaveBeenCalledWith(1);
         });
 
         it("when called with some items and the predicate resolves to false for one of them, it should return false", async () => {
-            const predicate = jest.fn().mockResolvedValueOnce(true).mockResolvedValueOnce(false);
+            const predicate = vi.fn().mockResolvedValueOnce(true).mockResolvedValueOnce(false);
             expect(await asyncEvery([1, 2, 3], predicate)).toBe(false);
             expect(predicate).toHaveBeenCalledTimes(2);
             expect(predicate).toHaveBeenCalledWith(1);
@@ -442,11 +444,11 @@ describe("arrays", () => {
 
     describe("asyncSome", () => {
         it("when called with an empty array, it should return false", async () => {
-            expect(await asyncSome([], jest.fn().mockResolvedValue(true))).toBe(false);
+            expect(await asyncSome([], vi.fn().mockResolvedValue(true))).toBe(false);
         });
 
         it("when called with some items and the predicate resolves to false for all of them, it should return false", async () => {
-            const predicate = jest.fn().mockResolvedValue(false);
+            const predicate = vi.fn().mockResolvedValue(false);
             expect(await asyncSome([1, 2, 3], predicate)).toBe(false);
             expect(predicate).toHaveBeenCalledTimes(3);
             expect(predicate).toHaveBeenCalledWith(1);
@@ -455,7 +457,7 @@ describe("arrays", () => {
         });
 
         it("when called with some items and the predicate resolves to true, it should short-circuit and return true", async () => {
-            const predicate = jest.fn().mockResolvedValueOnce(false).mockResolvedValueOnce(true);
+            const predicate = vi.fn().mockResolvedValueOnce(false).mockResolvedValueOnce(true);
             expect(await asyncSome([1, 2, 3], predicate)).toBe(true);
             expect(predicate).toHaveBeenCalledTimes(2);
             expect(predicate).toHaveBeenCalledWith(1);
@@ -465,30 +467,30 @@ describe("arrays", () => {
 
     describe("asyncSomeParallel", () => {
         it("when called with an empty array, it should return false", async () => {
-            expect(await asyncSomeParallel([], jest.fn().mockResolvedValue(true))).toBe(false);
+            expect(await asyncSomeParallel([], vi.fn().mockResolvedValue(true))).toBe(false);
         });
 
         it("when all the predicates return false", async () => {
-            expect(await asyncSomeParallel([1, 2, 3], jest.fn().mockResolvedValue(false))).toBe(false);
+            expect(await asyncSomeParallel([1, 2, 3], vi.fn().mockResolvedValue(false))).toBe(false);
         });
 
         it("when all the predicates return true", async () => {
-            expect(await asyncSomeParallel([1, 2, 3], jest.fn().mockResolvedValue(true))).toBe(true);
+            expect(await asyncSomeParallel([1, 2, 3], vi.fn().mockResolvedValue(true))).toBe(true);
         });
 
         it("when one of the predicate return true", async () => {
-            const predicate = jest.fn().mockImplementation((value) => Promise.resolve(value === 2));
+            const predicate = vi.fn().mockImplementation((value) => Promise.resolve(value === 2));
             expect(await asyncSomeParallel([1, 2, 3], predicate)).toBe(true);
         });
     });
 
     describe("asyncFilter", () => {
         it("when called with an empty array, it should return an empty array", async () => {
-            expect(await asyncFilter([], jest.fn().mockResolvedValue(true))).toEqual([]);
+            expect(await asyncFilter([], vi.fn().mockResolvedValue(true))).toEqual([]);
         });
 
         it("should filter the content", async () => {
-            const predicate = jest.fn().mockImplementation((value) => Promise.resolve(value === 2));
+            const predicate = vi.fn().mockImplementation((value) => Promise.resolve(value === 2));
             expect(await asyncFilter([1, 2, 3], predicate)).toEqual([2]);
         });
     });

apps/web/src/utils/colour.test.ts

@@ -6,7 +6,9 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
-import { textToHtmlRainbow } from "../../../src/utils/colour";
+import { describe, it, expect } from "vitest";
+
+import { textToHtmlRainbow } from "./colour";
 
 describe("textToHtmlRainbow", () => {
     it("correctly transform text to html without splitting the emoji in two", () => {

apps/web/src/utils/connection.test.ts

@@ -6,16 +6,17 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
+import { vi, describe, it, expect, beforeEach, type Mock } from "vitest";
 import { type ClientEvent, type ClientEventHandlerMap, SyncState } from "matrix-js-sdk/src/matrix";
 
-import { createReconnectedListener } from "../../../src/utils/connection";
+import { createReconnectedListener } from "./connection";
 
 describe("createReconnectedListener", () => {
     let reconnectedListener: ClientEventHandlerMap[ClientEvent.Sync];
-    let onReconnect: jest.Mock;
+    let onReconnect: Mock;
 
     beforeEach(() => {
-        onReconnect = jest.fn();
+        onReconnect = vi.fn();
         reconnectedListener = createReconnectedListener(onReconnect);
     });
 

apps/web/src/utils/enums.test.ts

@@ -6,7 +6,9 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
-import { getEnumValues, isEnumValue } from "../../../src/utils/enums";
+import { describe, it, expect } from "vitest";
+
+import { getEnumValues, isEnumValue } from "./enums";
 
 enum TestStringEnum {
     First = "__first__",

apps/web/src/utils/iterables.test.ts

@@ -6,7 +6,9 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
-import { iterableDiff, iterableIntersection } from "../../../src/utils/iterables";
+import { describe, it, expect } from "vitest";
+
+import { iterableDiff, iterableIntersection } from "./iterables";
 
 describe("iterables", () => {
     describe("iterableIntersection", () => {

apps/web/src/utils/keepIfSame.test.ts

@@ -5,7 +5,9 @@
  * Please see LICENSE files in the repository root for full details.
  */
 
-import { keepIfSame } from "../../../src/utils/keepIfSame";
+import { describe, it, expect } from "vitest";
+
+import { keepIfSame } from "./keepIfSame";
 
 describe("keepIfSame", () => {
     it("returns the next value if the current and next values are not deeply equal", () => {

apps/web/src/utils/objects.test.ts

@@ -6,6 +6,8 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
+import { describe, it, expect } from "vitest";
+
 import {
     objectClone,
     objectDiff,
@@ -14,7 +16,7 @@ import {
     objectKeyChanges,
     objectShallowClone,
     objectWithOnly,
-} from "../../../src/utils/objects";
+} from "./objects";
 
 describe("objects", () => {
     describe("objectExcluding", () => {

apps/web/src/utils/oidc/persistOidcSettings.test.ts

@@ -6,9 +6,11 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
+// @vitest-environment happy-dom
+
+import { vi, describe, it, expect, beforeEach } from "vitest";
 import { type IdTokenClaims } from "oidc-client-ts";
 import { decodeIdToken } from "matrix-js-sdk/src/matrix";
-import { mocked } from "jest-mock";
 
 import {
     getStoredOidcClientId,
@@ -16,13 +18,13 @@ import {
     getStoredOidcIdTokenClaims,
     getStoredOidcTokenIssuer,
     persistOidcAuthenticatedSettings,
-} from "../../../../src/utils/oidc/persistOidcSettings";
+} from "./persistOidcSettings";
 
-jest.mock("matrix-js-sdk/src/matrix");
+vi.mock("matrix-js-sdk/src/matrix");
 
 describe("persist OIDC settings", () => {
-    jest.spyOn(Storage.prototype, "getItem");
-    jest.spyOn(Storage.prototype, "setItem");
+    vi.spyOn(localStorage, "getItem");
+    vi.spyOn(localStorage, "setItem");
 
     beforeEach(() => {
         localStorage.clear();
@@ -101,7 +103,7 @@ describe("persist OIDC settings", () => {
 
         it("should return claims extracted from id_token in localStorage", () => {
             localStorage.setItem("mx_oidc_id_token", idToken);
-            mocked(decodeIdToken).mockReturnValue(idTokenClaims);
+            vi.mocked(decodeIdToken).mockReturnValue(idTokenClaims);
             expect(getStoredOidcIdTokenClaims()).toEqual(idTokenClaims);
             expect(decodeIdToken).toHaveBeenCalledWith(idToken);
             expect(localStorage.getItem).toHaveBeenCalledWith("mx_oidc_id_token_claims");

apps/web/src/utils/oidc/urls.test.ts

@@ -5,7 +5,9 @@ SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
 Please see LICENSE files in the repository root for full details.
 */
 
-import { getManageDeviceUrl } from "../../../../src/utils/oidc/urls";
+import { describe, it, expect } from "vitest";
+
+import { getManageDeviceUrl } from "./urls";
 
 describe("OIDC urls", () => {
     const accountManagementEndpoint = "https://auth.com/manage";

apps/web/src/utils/promise.test.ts

@@ -5,11 +5,13 @@
  * Please see LICENSE files in the repository root for full details.
  */
 
-import { batch } from "../../../src/utils/promise.ts";
+import { vi, describe, it, expect, afterEach } from "vitest";
+
+import { batch } from "./promise.ts";
 
 describe("promise.ts", () => {
     describe("batch", () => {
-        afterEach(() => jest.useRealTimers());
+        afterEach(() => vi.useRealTimers());
 
         it("should batch promises into groups of a given size", async () => {
             const promises = [() => Promise.resolve(1), () => Promise.resolve(2), () => Promise.resolve(3)];
@@ -19,7 +21,7 @@ describe("promise.ts", () => {
         });
 
         it("should wait for the current batch to finish to request the next one", async () => {
-            jest.useFakeTimers();
+            vi.useFakeTimers();
 
             let promise1Called = false;
             const promise1 = () =>
@@ -49,7 +51,7 @@ describe("promise.ts", () => {
             expect(promise2Called).toBe(true);
             expect(promise3Called).toBe(false);
 
-            jest.advanceTimersByTime(11);
+            vi.advanceTimersByTime(11);
             expect(await batchPromise).toEqual([1, 2, 3]);
         });
     });

apps/web/src/utils/sets.test.ts

@@ -6,7 +6,9 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
-import { setHasDiff } from "../../../src/utils/sets";
+import { describe, it, expect } from "vitest";
+
+import { setHasDiff } from "./sets";
 
 describe("sets", () => {
     describe("setHasDiff", () => {

apps/web/src/utils/stringOrderField.test.ts

@@ -6,10 +6,11 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
+import { describe, it, expect } from "vitest";
 import { sortBy } from "lodash";
 import { averageBetweenStrings, DEFAULT_ALPHABET } from "matrix-js-sdk/src/utils";
 
-import { midPointsBetweenStrings, reorderLexicographically } from "../../../src/utils/stringOrderField";
+import { midPointsBetweenStrings, reorderLexicographically } from "./stringOrderField";
 
 const moveLexicographicallyTest = (
     orders: Array<string | undefined>,

apps/web/src/utils/validate/numberInRange.test.ts

@@ -6,7 +6,9 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
-import { validateNumberInRange } from "../../../../src/utils/validate";
+import { describe, it, expect } from "vitest";
+
+import { validateNumberInRange } from "./numberInRange";
 
 describe("validateNumberInRange", () => {
     const min = 1;

apps/web/src/vector/getconfig.test.ts

@@ -6,9 +6,12 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
-import fetchMock from "@fetch-mock/jest";
+// @vitest-environment happy-dom
 
-import { getVectorConfig } from "../../../src/vector/getconfig";
+import { vi, describe, it, expect, beforeEach, afterAll } from "vitest";
+import fetchMock from "@fetch-mock/vitest";
+
+import { getVectorConfig } from "./getconfig";
 
 describe("getVectorConfig()", () => {
     const elementDomain = "app.element.io";
@@ -27,13 +30,13 @@ describe("getVectorConfig()", () => {
         });
 
         // stable value for cachebuster
-        jest.spyOn(Date, "now").mockReturnValue(now);
-        jest.clearAllMocks();
+        vi.spyOn(Date, "now").mockReturnValue(now);
+        vi.clearAllMocks();
         fetchMock.removeRoutes();
     });
 
     afterAll(() => {
-        jest.spyOn(Date, "now").mockRestore();
+        vi.spyOn(Date, "now").mockRestore();
     });
 
     it("requests specific config for document domain", async () => {

apps/web/src/vector/routing.test.ts

@@ -6,16 +6,20 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
-import { getInitialScreenAfterLogin, init, onNewScreen } from "../../../src/vector/routing";
-import type MatrixChat from "../../../src/components/structures/MatrixChat.tsx";
+// @vitest-environment happy-dom
+
+import { vi, describe, it, expect, beforeEach, afterAll } from "vitest";
+
+import { getInitialScreenAfterLogin, init, onNewScreen } from "./routing";
+import type MatrixChat from "../components/structures/MatrixChat.tsx";
 
 describe("onNewScreen", () => {
     it("should replace history if stripping via fields", () => {
         Object.defineProperty(window, "location", {
             value: {
                 hash: "#/room/!room:server?via=abc",
-                replace: jest.fn(),
-                assign: jest.fn(),
+                replace: vi.fn(),
+                assign: vi.fn(),
             },
             writable: true,
         });
@@ -28,8 +32,8 @@ describe("onNewScreen", () => {
         Object.defineProperty(window, "location", {
             value: {
                 hash: "#/room/!room1:server?via=abc",
-                replace: jest.fn(),
-                assign: jest.fn(),
+                replace: vi.fn(),
+                assign: vi.fn(),
             },
             writable: true,
         });
@@ -41,8 +45,8 @@ describe("onNewScreen", () => {
 
 describe("getInitialScreenAfterLogin", () => {
     beforeEach(() => {
-        jest.spyOn(sessionStorage.__proto__, "getItem").mockClear().mockReturnValue(null);
-        jest.spyOn(sessionStorage.__proto__, "setItem").mockClear();
+        vi.spyOn(sessionStorage, "getItem").mockClear().mockReturnValue(null);
+        vi.spyOn(sessionStorage, "setItem").mockClear();
     });
 
     const makeMockLocation = (hash = "") => {
@@ -65,7 +69,7 @@ describe("getInitialScreenAfterLogin", () => {
             const screen = {
                 screen: "/room/!test",
             };
-            jest.spyOn(sessionStorage.__proto__, "getItem").mockReturnValue(JSON.stringify(screen));
+            vi.spyOn(sessionStorage, "getItem").mockReturnValue(JSON.stringify(screen));
             expect(getInitialScreenAfterLogin(makeMockLocation())).toEqual(screen);
         });
     });
@@ -111,7 +115,7 @@ describe("init", () => {
         });
 
         window.matrixChat = {
-            showScreen: jest.fn(),
+            showScreen: vi.fn(),
         } as unknown as MatrixChat;
 
         init();

apps/web/src/vector/url_utils.test.ts

@@ -5,7 +5,9 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
-import { parseAppUrl, parseQsFromFragment, searchParamsToQueryDict } from "../../../src/vector/url_utils";
+import { describe, it, expect } from "vitest";
+
+import { parseAppUrl, parseQsFromFragment, searchParamsToQueryDict } from "./url_utils";
 
 // @ts-ignore
 const location: Location = {

apps/web/vitest.config.ts

@@ -0,0 +1,18 @@
+/*
+Copyright 2026 Element Creations Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE files in the repository root for full details.
+*/
+
+import { defineProject } from "vitest/config";
+
+export default defineProject({
+    test: {
+        include: ["src/**/*.test.{ts,tsx}"],
+        environment: "node",
+        pool: "threads",
+        globals: false,
+        setupFiles: ["src/test/setupTests.ts"],
+    },
+});