chore: migrate from jest to vitest

.github/workflows/unit.yml

@@ -64,12 +64,12 @@ jobs:
               run: yarn bundlesize
             - name: Check types
               run: yarn test:types
-            - name: Run Jest tests
+            - name: Run unit tests
               run: yarn test:ci
-            - name: Upload Jest coverage report
+            - name: Upload unit test coverage report
               uses: actions/upload-artifact@v3
               with:
-                  name: jest-coverage-report
+                  name: test-coverage-report
                   path: coverage/
             - name: Run benchmark smoke tests
               run: CHROME_BINARY=${{ steps.setup-chrome.outputs.chrome-path }} BENCHMARK_SMOKE_TEST=1 yarn test:performance

package.json

@@ -18,10 +18,10 @@
         "build:performance:benchmarks": "nx build @lwc/perf-benchmarks",
         "copy-fork": "./scripts/tasks/unsafe-external-contributor-ci-workaround.sh",
         "dev": "nx run-many --target=dev --all --parallel=999 --exclude=@lwc/perf-benchmarks,@lwc/perf-benchmarks-components,@lwc/integration-tests,lwc",
-        "test": "jest --config ./scripts/jest/root.config.js",
+        "test": "vitest --workspace vitest.workspace.mjs",
         "test:bespoke": "nx run-many --target=test",
-        "test:debug": "node --inspect node_modules/.bin/jest --config ./scripts/jest/root.config.js --runInBand --watch",
-        "test:ci": "yarn test --no-cache --coverage --runInBand",
+        "test:debug": "vitest --workspace vitest.workspace.mjs --inspect-brk --no-file-parallelism",
+        "test:ci": "vitest run --workspace vitest.workspace.mjs --coverage",
         "test:karma": "nx test @lwc/integration-karma",
         "test:integration": "nx sauce @lwc/integration-tests",
         "test:performance": "nx test @lwc/perf-benchmarks",
@@ -34,21 +34,21 @@
         "prettier": "v3 requires ESM, and we use prettier in our Jest tests. Jest does not support ESM yet."
     },
     "devDependencies": {
-        "@babel/plugin-transform-modules-commonjs": "^7.24.8",
         "@commitlint/cli": "^19.3.0",
         "@eslint/compat": "^1.1.1",
         "@eslint/js": "^9.7.0",
         "@lwc/eslint-plugin-lwc-internal": "link:./scripts/eslint-plugin",
-        "@lwc/jest-utils-lwc-internals": "link:./scripts/jest/utils",
+        "@lwc/test-utils-lwc-internals": "link:./scripts/test-utils",
         "@rollup/plugin-commonjs": "^26.0.1",
         "@rollup/plugin-inject": "^5.0.5",
         "@rollup/plugin-node-resolve": "^15.2.3",
         "@rollup/plugin-replace": "^5.0.7",
         "@rollup/plugin-typescript": "^11.1.6",
         "@types/babel__core": "^7.20.5",
-        "@types/jest": "^29.5.12",
         "@types/node": "^20.14.11",
         "@types/prettier": "^2.7.3",
+        "@vitest/coverage-v8": "^2.0.3",
+        "@vitest/ui": "^2.0.3",
         "bytes": "^3.1.2",
         "es-module-lexer": "^1.5.4",
         "eslint": "^9.7.0",
@@ -60,18 +60,17 @@
         "globals": "^15.8.0",
         "husky": "^9.1.1",
         "isbinaryfile": "^5.0.2",
-        "jest": "^29.7.0",
-        "jest-environment-jsdom": "^29.7.0",
+        "jsdom": "^24.1.1",
         "lint-staged": "^15.2.7",
         "magic-string": "^0.30.10",
         "nx": "19.5.1",
         "prettier": "^2.8.8",
         "rollup": "^4.19.0",
         "terser": "^5.31.3",
-        "ts-jest": "^29.2.3",
         "tslib": "^2.6.3",
         "typescript": "5.5.3",
-        "typescript-eslint": "^7.16.1"
+        "typescript-eslint": "^7.16.1",
+        "vitest": "^2.0.3"
     },
     "lint-staged": {
         "*.{js,mjs,ts}": "eslint",

packages/@lwc/babel-plugin-component/src/__tests__/index.spec.ts

@@ -8,7 +8,7 @@ import fs from 'node:fs';
 import path from 'node:path';
 import { transformSync } from '@babel/core';
 import { LWC_VERSION, HIGHEST_API_VERSION } from '@lwc/shared';
-import { testFixtureDir } from '@lwc/jest-utils-lwc-internals';
+import { testFixtureDir } from '@lwc/test-utils-lwc-internals';
 import plugin from '../index';
 
 const BASE_OPTS = {

packages/@lwc/babel-plugin-component/vitest.config.mjs

@@ -0,0 +1,20 @@
+import { mergeConfig, defineProject } from 'vitest/config';
+import sharedConfig from '../../../vitest.shared.mjs';
+import pkg from './package.json';
+
+export default mergeConfig(
+    sharedConfig,
+    defineProject({
+        test: {
+            name: 'babel-plugin-component',
+            // Workaround to fix `const enum`, which is required because we use e.g. `APIFeature` from `@lwc/shared`
+            // See https://github.com/vitest-dev/vitest/discussions/3964
+            // Using `src` also ensures that the test coverage is accurately reported
+            alias: Object.fromEntries(
+                Object.keys(pkg.dependencies ?? {})
+                    .filter((dep) => dep.startsWith('@lwc/'))
+                    .map((dep) => [dep, `${dep}/src`])
+            ),
+        },
+    })
+);

packages/@lwc/compiler/src/transformers/__tests__/transform-html.spec.ts

@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: MIT
  * For full license text, see the LICENSE file in the repo root or https://opensource.org/licenses/MIT
  */
+import { vi } from 'vitest';
 import { APIVersion, noop } from '@lwc/shared';
 import { TransformOptions } from '../../options';
 import { transformSync } from '../transformer';
@@ -199,12 +200,12 @@ describe('transformSync', () => {
                     ...TRANSFORMATION_OPTIONS,
                 })
             ).toThrowErrorMatchingInlineSnapshot(
-                '"LWC1128: Invalid lwc:dynamic usage. The LWC dynamic directive must be enabled in order to use this feature."'
+                `[Error: LWC1128: Invalid lwc:dynamic usage. The LWC dynamic directive must be enabled in order to use this feature.]`
             );
         });
 
         it('gathers metrics around use of the deprecated dynamic components', () => {
-            const incrementCounter = jest.fn();
+            const incrementCounter = vi.fn();
             const template = `
                 <template>
                     <x-dynamic lwc:dynamic={ctor}></x-dynamic>

packages/@lwc/compiler/src/transformers/__tests__/transform-javascript.spec.ts

@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: MIT
  * For full license text, see the LICENSE file in the repo root or https://opensource.org/licenses/MIT
  */
+import { vi } from 'vitest';
 import { noop } from '@lwc/shared';
 import { TransformOptions } from '../../options';
 import { transform, transformSync } from '../transformer';
@@ -121,7 +122,7 @@ it('should not apply babel plugins when Lightning Web Security is off', async ()
 
 describe('instrumentation', () => {
     it('should gather metrics for transforming dynamic imports', async () => {
-        const incrementCounter = jest.fn();
+        const incrementCounter = vi.fn();
         const actual = `
             export async function test() {
                 const x = await import("foo");

packages/@lwc/compiler/vitest.config.mjs

@@ -0,0 +1,20 @@
+import { defineProject, mergeConfig } from 'vitest/config';
+import baseConfig from '../../../vitest.shared.mjs';
+import pkg from './package.json';
+
+export default mergeConfig(
+    baseConfig,
+    defineProject({
+        test: {
+            name: 'lwc-compiler',
+            // Workaround to fix `const enum`, which is required because we use e.g. `APIFeature` from `@lwc/shared`
+            // See https://github.com/vitest-dev/vitest/discussions/3964
+            // Using `src` also ensures that the test coverage is accurately reported
+            alias: Object.fromEntries(
+                Object.keys(pkg.dependencies ?? {})
+                    .filter((dep) => dep.startsWith('@lwc/'))
+                    .map((dep) => [dep, `${dep}/src`])
+            ),
+        },
+    })
+);

packages/@lwc/engine-core/vitest.config.mjs

@@ -0,0 +1,20 @@
+import { defineProject, mergeConfig } from 'vitest/config';
+import baseConfig from '../../../vitest.shared.mjs';
+import pkg from './package.json';
+
+export default mergeConfig(
+    baseConfig,
+    defineProject({
+        test: {
+            name: 'lwc-engine-core',
+            // Workaround to fix `const enum`, which is required because we use e.g. `APIFeature` from `@lwc/shared`
+            // See https://github.com/vitest-dev/vitest/discussions/3964
+            // Using `src` also ensures that the test coverage is accurately reported
+            alias: Object.fromEntries(
+                Object.keys(pkg.dependencies ?? {})
+                    .filter((dep) => dep.startsWith('@lwc/'))
+                    .map((dep) => [dep, `${dep}/src`])
+            ),
+        },
+    })
+);

packages/@lwc/engine-dom/vitest.config.mjs

@@ -0,0 +1,21 @@
+import { defineProject, mergeConfig } from 'vitest/config';
+import baseConfig from '../../../vitest.shared.mjs';
+import pkg from './package.json';
+
+export default mergeConfig(
+    baseConfig,
+    defineProject({
+        test: {
+            name: 'lwc-engine-dom',
+            environment: 'jsdom',
+            // Workaround to fix `const enum`, which is required because we use e.g. `APIFeature` from `@lwc/shared`
+            // See https://github.com/vitest-dev/vitest/discussions/3964
+            // Using `src` also ensures that the test coverage is accurately reported
+            alias: Object.fromEntries(
+                Object.keys(pkg.dependencies ?? {})
+                    .filter((dep) => dep.startsWith('@lwc/'))
+                    .map((dep) => [dep, `${dep}/src`])
+            ),
+        },
+    })
+);

packages/@lwc/engine-server/src/__tests__/fixtures.spec.ts

@@ -10,7 +10,8 @@ import path from 'path';
 
 import { rollup } from 'rollup';
 import lwcRollupPlugin from '@lwc/rollup-plugin';
-import { testFixtureDir, formatHTML } from '@lwc/jest-utils-lwc-internals';
+import { vi } from 'vitest';
+import { testFixtureDir, formatHTML } from '@lwc/test-utils-lwc-internals';
 import type * as lwc from '../index';
 
 interface FixtureModule {
@@ -20,7 +21,17 @@ interface FixtureModule {
     features?: any[];
 }
 
-jest.setTimeout(10_000 /* 10 seconds */);
+vi.setConfig({ testTimeout: 10_000 /* 10 seconds */ });
+
+vi.mock('lwc', async () => {
+    const lwcEngineServer = await import('../index');
+    lwcEngineServer!.setHooks({
+        sanitizeHtmlContent(content: unknown) {
+            return content as string;
+        },
+    });
+    return lwcEngineServer;
+});
 
 async function compileFixture({ input, dirname }: { input: string; dirname: string }) {
     const modulesDir = path.resolve(dirname, './modules');
@@ -49,7 +60,7 @@ async function compileFixture({ input, dirname }: { input: string; dirname: stri
 
     await bundle.write({
         file: outputFile,
-        format: 'cjs',
+        format: 'esm',
         exports: 'named',
     });
 
@@ -80,24 +91,14 @@ function testFixtures() {
             // On top of this, the engine also checks if the component constructor is an instance of
             // the LightningElement. Therefor the compiled module should also be evaluated in the
             // same sandbox registry as the engine.
-            let lwcEngineServer: typeof lwc | undefined;
-            let module: FixtureModule | undefined;
-            jest.isolateModules(() => {
-                lwcEngineServer = require('../index');
-                module = require(compiledFixturePath);
-            });
+            const lwcEngineServer = await import('../index');
+            const module = (await import(compiledFixturePath)) as FixtureModule;
 
             const features = module!.features ?? [];
             features.forEach((flag) => {
                 lwcEngineServer!.setFeatureFlagForTest(flag, true);
             });
 
-            lwcEngineServer!.setHooks({
-                sanitizeHtmlContent(content: unknown) {
-                    return content as string;
-                },
-            });
-
             let result;
             let err;
             try {

packages/@lwc/engine-server/src/__tests__/html-serialization.spec.ts

@@ -12,6 +12,7 @@ import { rollup, RollupLog } from 'rollup';
 import replace from '@rollup/plugin-replace';
 import virtual from '@rollup/plugin-virtual';
 import lwcRollupPlugin from '@lwc/rollup-plugin';
+import { vi } from 'vitest';
 import * as engineServer from '../index';
 
 /**
@@ -20,7 +21,7 @@ import * as engineServer from '../index';
  * robust than snapshots, which may have invalid/incorrect HTML.
  */
 
-jest.setTimeout(10_000 /* 10 seconds */);
+vi.setConfig({ testTimeout: 10_000 /* 10 seconds */ });
 
 // Compile a component to an HTML string, using the full LWC compilation pipeline
 async function compileComponent(tagName: string, componentName: string) {

packages/@lwc/engine-server/vitest.config.mjs

@@ -0,0 +1,20 @@
+import { defineProject, mergeConfig } from 'vitest/config';
+import baseConfig from '../../../vitest.shared.mjs';
+import pkg from './package.json';
+
+export default mergeConfig(
+    baseConfig,
+    defineProject({
+        test: {
+            name: 'lwc-engine-server',
+            // Workaround to fix `const enum`, which is required because we use e.g. `APIFeature` from `@lwc/shared`
+            // See https://github.com/vitest-dev/vitest/discussions/3964
+            // Using `src` also ensures that the test coverage is accurately reported
+            alias: Object.fromEntries(
+                Object.keys(pkg.dependencies ?? {})
+                    .filter((dep) => dep.startsWith('@lwc/'))
+                    .map((dep) => [dep, `${dep}/src`])
+            ),
+        },
+    })
+);