feat(mock): support `spy: true` option in `rs.mock()` by 9aoy · Pull Request #901 · web-infra-dev/rstest

9aoy · 2026-01-23T07:58:34Z

Summary

Support the { spy: true } option in rs.mock() and related APIs, allowing modules to be auto-mocked while preserving their original implementations.

import { add, multiply } from './math';

rs.mock('./math', { spy: true });

test('spy mode preserves implementation', () => {
  expect(add(1, 2)).toBe(3); // Original works
  expect(add).toHaveBeenCalledWith(1, 2); // Can assert calls
  
  // Can also override with mockImplementation/mockReturnValue
  rs.mocked(add).mockReturnValueOnce(100);
  expect(add(1, 2)).toBe(100);
  expect(add(1, 2)).toBe(3); // Back to original
});

Features

Add { spy: true } option to rs.mock, rs.doMock, rs.mockRequire, rs.doMockRequire
When spy: true, all module exports are wrapped in spy functions that:
- Track calls (can use toHaveBeenCalled, toHaveBeenCalledWith, etc.)
- Still execute the original implementation
Add MockModuleOptions type with literal { spy: true } (throws error for invalid values)

Changes

packages/core/src/types/mock.ts: Add MockModuleOptions type
packages/core/src/core/plugins/mockRuntimeCode.js: Handle { spy: true } option in 4 mock functions
e2e/mock/tests/mockSpy.test.ts: E2E tests for spy mode
e2e/mock/tests/doMockSpy.test.ts: E2E tests for doMock with spy
website/docs/*/api/runtime-api/rstest/mock-modules.mdx: Documentation updates
website/docs/*/api/runtime-api/rstest/mock-functions.mdx: Documentation updates
website/AGENTS.md: Add heading-case guideline

- Add `{ spy: true }` option to `rs.mock`, `rs.doMock`, `rs.mockRequire`, `rs.doMockRequire` - When `spy: true`, module is auto-mocked but original implementations are preserved - All exports are wrapped in spy functions that track calls while executing original code - Add `MockModuleOptions` type with literal `{ spy: true }` (throws error for other values) - Add e2e tests for spy mode with mockImplementation, mockReturnValue, unmock - Update documentation with examples for factory function, rs.fn(), rs.mockObject(), and partial mock

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Pull request overview

Adds { spy: true } support to rs.mock()-family APIs so modules can be auto-mocked while preserving original implementations, with documentation and e2e coverage.

Changes:

Extend core typings to accept { spy: true } for module mocking APIs.
Implement spy-mode handling in the webpack runtime mock hooks.
Add e2e tests and update EN/ZH docs for the new spy behavior.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
`packages/core/src/types/mock.ts`	Introduces `MockModuleOptions` and updates `rs.mock`/`doMock`/`mockRequire`/`doMockRequire` signatures to accept `{ spy: true }`.
`packages/core/src/core/plugins/mockRuntimeCode.js`	Adds runtime support for `{ spy: true }` across 4 mock entry points by wrapping original exports via `mockObject(..., { spy: true })`.
`e2e/mock/tests/mockSpy.test.ts`	Adds e2e coverage for `rs.mock(..., { spy: true })` behavior (call tracking + preserving implementation).
`e2e/mock/tests/doMockSpy.test.ts`	Adds e2e coverage for `rs.doMock(..., { spy: true })` behavior.
`website/docs/en/api/runtime-api/rstest/mock-modules.mdx`	Documents `{ spy: true }` usage and reorganizes module mocking docs.
`website/docs/zh/api/runtime-api/rstest/mock-modules.mdx`	Same documentation updates for ZH.
`website/docs/en/api/runtime-api/rstest/mock-functions.mdx`	Updates examples to use `{ spy: true }` in the module-mocking context.
`website/docs/zh/api/runtime-api/rstest/mock-functions.mdx`	Same example update for ZH.
`website/AGENTS.md`	Adds sentence-style heading capitalization guideline.

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packages/core/src/core/plugins/mockRuntimeCode.js

Copilot · 2026-01-23T08:13:19Z

packages/core/src/core/plugins/mockRuntimeCode.js

+      __webpack_require__.r(__webpack_exports__);
+      for (const key in mockedModule) {
+        __webpack_require__.d(__webpack_exports__, {
+          [key]: () => mockedModule[key],
+        });


rs.mock(..., { spy: true }) marks the replacement as an ESM module (__webpack_require__.r(__webpack_exports__)) and only re-exports enumerable keys from mockedModule. For CommonJS targets (where consumers use default-import interop via __webpack_require__.n), this can break import x from 'cjs-module' because there is no default export defined. Consider adding a default export (e.g., mapping to the spied module) when the original module is not __esModule, to preserve default-import behavior.

packages/core/src/core/plugins/mockRuntimeCode.js

Copilot · 2026-01-23T08:13:20Z

e2e/mock/tests/mockSpy.test.ts

+    rs.mocked(increment).mockReturnValueOnce(111);
+    rs.mocked(increment).mockReturnValueOnce(222);
+
+    expect(increment(1)).toBe(111);
+    expect(increment(1)).toBe(222);
+    // Falls back to previous mockReturnValue(999)


This test is order-dependent: it expects the third call to fall back to a mockReturnValue(999) configured in a previous test. If tests are reordered or run with isolation, this can become flaky. Set the baseline mockReturnValue within this test (or reset+configure in a beforeEach) so the test is self-contained.

Suggested change

rs.mocked(increment).mockReturnValueOnce(111);

rs.mocked(increment).mockReturnValueOnce(222);

expect(increment(1)).toBe(111);

expect(increment(1)).toBe(222);

// Falls back to previous mockReturnValue(999)

rs.mocked(increment).mockReturnValue(999);

rs.mocked(increment).mockReturnValueOnce(111);

rs.mocked(increment).mockReturnValueOnce(222);

expect(increment(1)).toBe(111);

expect(increment(1)).toBe(222);

// Falls back to baseline mockReturnValue(999) set in this test

Copilot · 2026-01-23T08:13:20Z

e2e/mock/tests/doMockSpy.test.ts

+    expect(increment).toHaveBeenCalledTimes(2);
+    expect(increment).toHaveBeenCalledWith(1);
+    expect(increment).toHaveBeenCalledWith(5);
+    expect(rs.isMockFunction(increment)).toBe(true);


These assertions can be flaky if this file’s tests run in a different order: rs.doMock(..., { spy: true }) may reuse an existing mock function (mockObject returns existing _isMockFunction values as-is), so call history can carry over between tests and make toHaveBeenCalledTimes(2) fail. Consider resetting mocks/modules (e.g., rs.resetAllMocks() / rs.resetModules() / rs.doUnmock(...)) in beforeEach/afterEach to keep tests isolated.

Copilot AI review requested due to automatic review settings January 23, 2026 07:58

github-actions bot added the change: feat label Jan 23, 2026

Copilot started reviewing on behalf of 9aoy January 23, 2026 07:58 View session

9aoy changed the title ~~feat(mock): support rs.mock('module', { spy: true }) option~~ feat(mock): support spy: true option in rs.mock() Jan 23, 2026

Copilot AI reviewed Jan 23, 2026

View reviewed changes

fix: cjs module

3eb17ff

9aoy merged commit 5a769dd into main Jan 26, 2026
10 checks passed

9aoy deleted the mockSpy branch January 26, 2026 09:04

9aoy mentioned this pull request Jan 27, 2026

release: 0.8.1 #908

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feat(mock): support `spy: true` option in `rs.mock()`#901

feat(mock): support `spy: true` option in `rs.mock()`#901
9aoy merged 2 commits intomainfrom
mockSpy

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9aoy commented Jan 23, 2026 •

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