feat(core): add `mockObject` and `mocked` utilities by 9aoy · Pull Request #881 · web-infra-dev/rstest

9aoy · 2026-01-19T12:43:52Z

Summary

Add rs.mockObject() for deep mocking objects with optional spy mode
Add rs.mocked() type helper for TypeScript mock type inference

class UserService {
  getUser() {
    return { id: 1, name: 'Alice' };
  }
}

const MockedService = rstest.mockObject(UserService);
const instance = new MockedService();

rs.mocked(instance.getUser).mockImplementation(() => ({ id: 2, name: 'Bob' }));
expect(instance.getUser()).toEqual({ id: 2, name: 'Bob' });

Checklist

Tests updated (or not required).
Documentation updated (or not required).

- Add rs.mockObject() for deep mocking objects with optional spy mode - Add rs.mocked() type helper for TypeScript mock type inference - Support mocking class constructors with proper ES6 class handling - Add MockedClass, MaybeMockedDeep, and related types - Add documentation for both English and Chinese - Add e2e tests for mockObject functionality

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Pull request overview

This pull request adds two new utilities to the rstest testing framework: mockObject for deep mocking objects with optional spy mode, and mocked as a TypeScript type helper for mock type inference.

Changes:

Adds mockObject() function that deeply mocks objects, replacing methods with mock functions while preserving primitive values
Adds mocked() type helper that provides proper TypeScript types for mocked objects without runtime behavior changes
Includes comprehensive type definitions for mocking classes, functions, and nested objects

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 10 comments.

Show a summary per file

File	Description
packages/core/src/types/mock.ts	Defines type interfaces for MockOptions, MockedClass, MockedFunction, MockedObject, and helper types for deep mocking
packages/core/src/runtime/api/mockObject.ts	Implements the core mockObject algorithm with circular reference handling, getter/setter support, and deep property traversal
packages/core/src/runtime/api/spy.ts	Adds createMockInstance function for handling class constructors and prototype methods
packages/core/src/runtime/api/utilities.ts	Integrates mockObject and mocked utilities into the rstest API
e2e/mock/tests/mockObject.test.ts	Provides test coverage for basic mocking, spy mode, arrays, primitives, objects, classes, and the mocked helper
website/docs/en/api/runtime-api/rstest/mock-functions.mdx	Documents mockObject and mocked with usage examples in English
website/docs/zh/api/runtime-api/rstest/mock-functions.mdx	Documents mockObject and mocked with usage examples in Chinese

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Copilot · 2026-01-19T12:48:34Z

e2e/mock/tests/mockObject.test.ts

+import { describe, expect, rs, test } from '@rstest/core';
+
+describe('rs.mockObject', () => {
+  test('mocks methods to return undefined by default', () => {
+    const mocked = rs.mockObject({
+      method() {
+        return 42;
+      },
+    });
+
+    expect(mocked.method()).toBe(undefined);
+    expect(rs.isMockFunction(mocked.method)).toBe(true);
+  });
+
+  test('keeps method name', () => {
+    const mocked = rs.mockObject({
+      myMethod() {
+        return 42;
+      },
+    });
+
+    expect(mocked.myMethod.getMockName()).toBe('myMethod');
+  });
+
+  test('mocks nested objects deeply', () => {
+    const original = {
+      simple: () => 'value',
+      nested: {
+        method: () => 'real',
+      },
+      prop: 'foo',
+    };
+
+    const mocked = rs.mockObject(original);
+    expect(mocked.simple()).toBe(undefined);
+    expect(mocked.nested.method()).toBe(undefined);
+    expect(mocked.prop).toBe('foo');
+  });
+
+  test('can mock return values', () => {
+    const mocked = rs.mockObject({
+      simple: (): string => 'value',
+      nested: {
+        method: (): string => 'real',
+      },
+    });
+
+    mocked.simple.mockReturnValue('mocked');
+    mocked.nested.method.mockReturnValue('mocked nested');
+
+    expect(mocked.simple()).toBe('mocked');
+    expect(mocked.nested.method()).toBe('mocked nested');
+  });
+
+  test('with spy option keeps original implementations', () => {
+    const original = {
+      simple: () => 'value',
+      nested: {
+        method: () => 'real',
+      },
+    };
+
+    const spied = rs.mockObject(original, { spy: true });
+    expect(spied.simple()).toBe('value');
+    expect(spied.simple).toHaveBeenCalled();
+    expect(spied.simple.mock.results[0]).toEqual({
+      type: 'return',
+      value: 'value',
+    });
+  });
+
+  test('arrays are empty by default', () => {
+    const { array } = rs.mockObject({
+      array: [1, 2, 3],
+    });
+    expect(array).toEqual([]);
+  });
+
+  test('arrays keep values when spy is true', () => {
+    const { array } = rs.mockObject(
+      {
+        array: [1, 2, 3],
+      },
+      { spy: true },
+    );
+    expect(array).toHaveLength(3);
+    expect(array[0]).toBe(1);
+    expect(array[1]).toBe(2);
+    expect(array[2]).toBe(3);
+  });
+
+  test('keeps primitive values', () => {
+    const mocked = rs.mockObject({
+      number: 123,
+      string: 'hello',
+      boolean: true,
+      nullValue: null,
+    });
+
+    expect(mocked.number).toBe(123);
+    expect(mocked.string).toBe('hello');
+    expect(mocked.boolean).toBe(true);
+    expect(mocked.nullValue).toBe(null);
+  });
+
+  test('deeply clones objects', () => {
+    const mocked = rs.mockObject({
+      obj: { a: 1, b: { c: 2 } },
+    });
+
+    expect(mocked.obj).toEqual({ a: 1, b: { c: 2 } });
+  });
+
+  test('mocks class constructors', () => {
+    class OriginalClass {
+      value = 42;
+      getValue() {
+        return this.value;
+      }
+    }
+    const MockedClass = rs.mockObject(OriginalClass, { spy: true });
+    const instance = new MockedClass();
+    expect(instance.getValue()).toBe(42);
+    rs.mocked(instance.getValue).mockImplementation(() => 100);
+    expect(instance.getValue()).toBe(100);
+  });
+});
+
+describe('rs.mocked', () => {
+  test('returns the same object', () => {
+    const mock = rs.fn();
+    const mocked = rs.mocked(mock);
+    expect(mocked).toBe(mock);
+  });
+
+  test('works with deep option', () => {
+    const mock = rs.fn();
+    const mocked = rs.mocked(mock, true);
+    expect(mocked).toBe(mock);
+  });
+
+  test('works with options object', () => {
+    const mock = rs.fn();
+    const mocked = rs.mocked(mock, { partial: true, deep: true });
+    expect(mocked).toBe(mock);
+  });
+});


The mockObject implementation handles special object types like Date, RegExp, and Map by returning them as-is (line 249 in mockObject.ts), but there are no tests verifying this behavior. Consider adding tests for these special object types to ensure they are handled correctly in both automock and autospy modes.

Copilot · 2026-01-19T12:48:34Z

website/docs/en/api/runtime-api/rstest/mock-functions.mdx

+```ts
+class UserService {
+  getUser() {
+    return { id: 1, name: 'Alice' };
+  }
+}
+
+const MockedService = rstest.mockObject(UserService);
+const instance = new MockedService();
+
+rs.mocked(instance.getUser).mockImplementation(() => ({ id: 2, name: 'Bob' }));
+expect(instance.getUser()).toEqual({ id: 2, name: 'Bob' });
+```


The documentation example for mocking classes doesn't specify the spy option, but the corresponding test (line 121) shows it requires { spy: true } to work correctly. Without the spy option, the class methods would return undefined and wouldn't preserve instance state. Consider either updating the documentation to include the spy option or clarifying that the example assumes spy mode.

website/docs/zh/api/runtime-api/rstest/mock-functions.mdx

Copilot · 2026-01-19T12:48:35Z

packages/core/src/runtime/api/utilities.ts

+        { value },
+        {},
+      ).value as MaybeMockedDeep<T>;


The mockObject function is called with the value wrapped in an object { value } and then extracts the value property from the result. This adds unnecessary complexity and could be simplified by passing the value directly to mockObject and having it return the mocked value directly, rather than wrapping and unwrapping.

Suggested change

{ value },

{},

).value as MaybeMockedDeep<T>;

value,

{},

) as MaybeMockedDeep<T>;

packages/core/src/runtime/api/mockObject.ts

e2e/mock/tests/mockObject.test.ts

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…ock-object

Copilot AI review requested due to automatic review settings January 19, 2026 12:43

github-actions bot added the change: feat label Jan 19, 2026

Copilot started reviewing on behalf of 9aoy January 19, 2026 12:44 View session

Copilot AI reviewed Jan 19, 2026

View reviewed changes

fix: update

a0ac95a

9aoy added 3 commits January 20, 2026 11:24

fix: lint

37f866b

fix: lint

5096357

Merge branch 'main' of https://github.com/web-infra-dev/rstest into m…

b8bee28

…ock-object

9aoy merged commit 6e563ff into main Jan 23, 2026
10 checks passed

9aoy deleted the mock-object branch January 23, 2026 04:49

9aoy mentioned this pull request Jan 27, 2026

release: 0.8.1 #908

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feat(core): add `mockObject` and `mocked` utilities#881

feat(core): add `mockObject` and `mocked` utilities#881
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