test(jest): add Jest to CI matrix (#372)

.github/workflows/release.yml

@@ -25,7 +25,7 @@ jobs:
       matrix:
         node: ['16', '18', '20']
         svelte: ['3', '4']
-        test-runner: ['vitest:jsdom', 'vitest:happy-dom']
+        test-runner: ['vitest:jsdom', 'vitest:happy-dom', 'jest']
         experimental: [false]
         include:
           - node: '20'
@@ -36,6 +36,10 @@ jobs:
             svelte: 'next'
             test-runner: 'vitest:happy-dom'
             experimental: true
+          - node: '20'
+            svelte: 'next'
+            test-runner: 'jest'
+            experimental: true
 
     steps:
       - name: ⬇️ Checkout repo
@@ -55,7 +59,7 @@ jobs:
         run: npm run test:${{ matrix.test-runner }}
 
       - name: ▶️ Run type-checks
-        if: ${{ matrix.node == '20' && matrix.svelte == '4' }}
+        if: ${{ matrix.node == '20' && matrix.svelte == '4' && matrix.test-runner == 'vitest:jsdom' }}
         run: npm run types
 
       - name: ⬆️ Upload coverage report

jest.config.js

@@ -0,0 +1,23 @@
+import { VERSION as SVELTE_VERSION } from 'svelte/compiler'
+
+const IS_SVELTE_5 = SVELTE_VERSION >= '5'
+
+export default {
+  testMatch: ['<rootDir>/src/__tests__/**/*.test.js'],
+  transform: {
+    '^.+\\.svelte$': 'svelte-jester',
+  },
+  moduleFileExtensions: ['js', 'svelte'],
+  extensionsToTreatAsEsm: ['.svelte'],
+  testEnvironment: 'jsdom',
+  setupFilesAfterEnv: ['<rootDir>/src/__tests__/_jest-setup.js'],
+  injectGlobals: false,
+  moduleNameMapper: {
+    '^vitest$': '<rootDir>/src/__tests__/_jest-vitest-alias.js',
+    '^@testing-library/svelte$': IS_SVELTE_5
+      ? '<rootDir>/src/svelte5-index.js'
+      : '<rootDir>/src/index.js',
+  },
+  resetMocks: true,
+  restoreMocks: true,
+}

package.json

@@ -67,6 +67,7 @@
     "test:watch": "vitest",
     "test:vitest:jsdom": "vitest run --coverage --environment jsdom",
     "test:vitest:happy-dom": "vitest run --coverage --environment happy-dom",
+    "test:jest": "npx --node-options=\"--experimental-vm-modules --no-warnings\" jest --coverage",
     "types": "svelte-check",
     "validate": "npm-run-all test:vitest:* types",
     "contributors:add": "all-contributors add",
@@ -89,6 +90,7 @@
     "@testing-library/dom": "^10.0.0"
   },
   "devDependencies": {
+    "@jest/globals": "^29.7.0",
     "@sveltejs/vite-plugin-svelte": "^3.0.2",
     "@testing-library/jest-dom": "^6.3.0",
     "@testing-library/user-event": "^14.5.2",
@@ -109,6 +111,8 @@
     "eslint-plugin-vitest-globals": "1.5.0",
     "expect-type": "^0.19.0",
     "happy-dom": "^14.7.1",
+    "jest": "^29.7.0",
+    "jest-environment-jsdom": "^29.7.0",
     "jsdom": "^24.0.0",
     "npm-run-all": "^4.1.5",
     "prettier": "3.2.5",

src/__tests__/_jest-setup.js

@@ -0,0 +1,9 @@
+import '@testing-library/jest-dom/jest-globals'
+
+import { afterEach } from '@jest/globals'
+import { act, cleanup } from '@testing-library/svelte'
+
+afterEach(async () => {
+  await act()
+  cleanup()
+})

src/__tests__/_jest-vitest-alias.js

@@ -0,0 +1,25 @@
+import { describe, jest, test } from '@jest/globals'
+
+export {
+  afterAll,
+  afterEach,
+  beforeAll,
+  beforeEach,
+  describe,
+  expect,
+  test,
+  jest as vi,
+} from '@jest/globals'
+
+// Add support for describe.skipIf and test.skipIf
+describe.skipIf = (condition) => (condition ? describe.skip : describe)
+test.skipIf = (condition) => (condition ? test.skip : test)
+
+// Add support for `stubGlobal`
+jest.stubGlobal = (property, stub) => {
+  if (typeof stub === 'function') {
+    jest.spyOn(globalThis, property).mockImplementation(stub)
+  } else {
+    jest.replaceProperty(globalThis, property, stub)
+  }
+}

src/__tests__/cleanup.test.js

@@ -19,7 +19,7 @@ describe('cleanup', () => {
     renderSubject()
     cleanup()
 
-    expect(onDestroyed).toHaveBeenCalledOnce()
+    expect(onDestroyed).toHaveBeenCalledTimes(1)
   })
 
   test('cleanup handles unexpected errors during mount', () => {

src/__tests__/mount.test.js

@@ -15,7 +15,7 @@ describe('mount and destroy', () => {
 
     expect(content).toBeInTheDocument()
     await act()
-    expect(onMounted).toHaveBeenCalledOnce()
+    expect(onMounted).toHaveBeenCalledTimes(1)
   })
 
   test('component is destroyed', async () => {
@@ -28,6 +28,6 @@ describe('mount and destroy', () => {
 
     expect(content).not.toBeInTheDocument()
     await act()
-    expect(onDestroyed).toHaveBeenCalledOnce()
+    expect(onDestroyed).toHaveBeenCalledTimes(1)
   })
 })

src/__tests__/rerender.test.js

@@ -23,7 +23,7 @@ describe('rerender', () => {
     await rerender({ props: { name: 'Dolly' } })
 
     expect(element).toHaveTextContent('Hello Dolly!')
-    expect(console.warn).toHaveBeenCalledOnce()
+    expect(console.warn).toHaveBeenCalledTimes(1)
     expect(console.warn).toHaveBeenCalledWith(
       expect.stringMatching(/deprecated/iu)
     )