René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"experimental-test-module-mocks with ES imports does not reset mocked modules for tests in the same file","articleBody":"### Version\n\n24.4.1\n\n### Platform\n\n```text\nMicrosoft Windows NT 10.0.26100.0 x64\n```\n\n### Subsystem\n\nnode:test\n\n### What steps will reproduce the bug?\n\n```javascript\n// file1: utils/fs-wrapper.js\n// Simple wrapper around fs.readFileSync to demonstrate the issue\nimport { readFileSync } from 'node:fs';\n\nexport default function readFile(path: string): string {\n    return readFileSync(path, 'utf8');\n}\n\n// file2: utils/file-processor.js\n// Module that depends on fs-wrapper\nimport readFile from './fs-wrapper.js';\n\nexport default function processFile(path: string): string {\n    const content = readFile(path);\n    return content.toUpperCase();\n}\n\n// file3: test/cache-issue.test.js\n// Test demonstrating the ES module cache issue\nimport { test, describe, beforeEach, mock } from 'node:test';\nimport assert from 'node:assert/strict';\n\ndescribe('ES Module Cache Issue with mock.restoreAll()', () =\u003e {\n    beforeEach(() =\u003e {\n        mock.restoreAll();\n    });\n\n    test('first test - should use mock', async (t) =\u003e {\n        // Mock the fs-wrapper module\n        const mockReadFile = mock.fn(() =\u003e 'mocked content from test 1');\n        t.mock.module('../utils/fs-wrapper.js', {\n            defaultExport: mockReadFile,\n        });\n\n        // Import the module that depends on fs-wrapper\n        const fileProcessorModule = await import('../utils/file-processor.js');\n        const processFile = fileProcessorModule.default;\n\n        const result = processFile('dummy-path.txt');\n\n        assert.strictEqual(result, 'MOCKED CONTENT FROM TEST 1');\n        assert.strictEqual(mockReadFile.mock.callCount(), 1);\n    });\n\n    test('second test - should use different mock but fails due to cache', async (t) =\u003e {\n        // Mock with different return value\n        const mockReadFile = mock.fn(() =\u003e 'mocked content from test 2');\n        t.mock.module('../utils/fs-wrapper.js', {\n            defaultExport: mockReadFile,\n        });\n\n        // This import returns cached version that still references the old mock\n        const fileProcessorModule = await import('../utils/file-processor.js');\n        const processFile = fileProcessorModule.default;\n\n        const result = processFile('dummy-path.txt');\n\n        // This assertion will fail because the cached module still uses the old mock\n        assert.strictEqual(result, 'MOCKED CONTENT FROM TEST 2');\n        assert.strictEqual(mockReadFile.mock.callCount(), 1);\n    });\n\n    test('third test - workaround with cache busting', async (t) =\u003e {\n        // Mock with third return value\n        const mockReadFile = mock.fn(() =\u003e 'mocked content from test 3');\n        t.mock.module('../utils/fs-wrapper.js', {\n            defaultExport: mockReadFile,\n        });\n\n        // Use cache busting query parameter to force fresh import\n        const fileProcessorModule = await import('../utils/file-processor.js?v=' + Date.now());\n        const processFile = fileProcessorModule.default;\n\n        const result = processFile('dummy-path.txt');\n\n        // This assertion passes because we bypassed the cache\n        assert.strictEqual(result, 'MOCKED CONTENT FROM TEST 3');\n        assert.strictEqual(mockReadFile.mock.callCount(), 1);\n    });\n});\n\n// Command line: node --test --experimental-test-module-mocks\n```\n\n### How often does it reproduce? Is there a required condition?\n\nEvery time.\n\n### What is the expected behavior? Why is that the expected behavior?\n\nThe mocked module should reset between tests.\n\n### What do you see instead?\n\n```\n▶ ES Module Cache Issue with mock.restoreAll()\n  ✔ first test - should use mock (43.5241ms)\n  ✖ second test - should use different mock but fails due to cache (3.0297ms)\n  ✔ third test - workaround with cache busting (4.2197ms)\n✖ ES Module Cache Issue with mock.restoreAll() (52.1751ms)\nℹ tests 6\nℹ suites 1\nℹ pass 5\nℹ fail 1\nℹ cancelled 0\nℹ skipped 0\nℹ todo 0\nℹ duration_ms 137.1057\n\n✖ failing tests:\n\ntest at dist\\tests\\file-processor.test.js:22:5\n✖ second test - should use different mock but fails due to cache (3.0297ms)\n  AssertionError [ERR_ASSERTION]: Expected values to be strictly equal:\n  actual expected\n\n      at TestContext.\u003canonymous\u003e (file:///C:/Users/xxx/Documents/GitHub/genesys-concepts/dist/tests/file-processor.test.js:34:16)\n      at async Test.run (node:internal/test_runner/test:1069:7)\n      at async Suite.processPendingSubtests (node:internal/test_runner/test:752:7) {\n    generatedMessage: true,\n    code: 'ERR_ASSERTION',\n    actual: 'MOCKED CONTENT FROM TEST 1',\n    expected: 'MOCKED CONTENT FROM TEST 2',\n    operator: 'strictEqual'\n  }\n```\n\n### Additional information\n\nNot sure if there is a better workaround for this or maybe I'm doing something wrong?","author":{"url":"https://github.com/Safricloud","@type":"Person","name":"Safricloud"},"datePublished":"2025-07-22T09:53:02.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":9},"url":"https://github.com/59163/node/issues/59163"}