🎭 Advanced Mocking

Production mocking patterns.

Partial Mocking

jest.mock('./utils', () => ({
  ...jest.requireActual('./utils'),
  getUser: jest.fn()
}));

test('uses partial mock', () => {
  getUser.mockReturnValue({ name: 'Alice' });
  // Other utils functions work normally
});

Mocking Multiple Calls

test('handles different responses', () => {
  const mockFn = jest.fn()
    .mockResolvedValueOnce({ status: 'pending' })
    .mockResolvedValueOnce({ status: 'complete' });
  
  expect(await mockFn()).toEqual({ status: 'pending' });
  expect(await mockFn()).toEqual({ status: 'complete' });
});

Module Mocking with Side Effects

jest.mock('./analytics', () => ({
  track: jest.fn(),
  init: jest.fn()
}));

test('initializes analytics', () => {
  import('./analytics').then(module => {
    expect(module.init).toHaveBeenCalled();
  });
});

✅ Key Takeaways

• Use **partial mocking** to mock selectively

• Mock **multiple calls** with different responses

• Handle **side effects** in mocks

• Keep mocks **close to reality**