Jest中如何模拟函数内部的函数调用？嵌套函数测试场景

Hey there! I see you're setting up tests for this nested function call chain (getBookingStateObject → getBookingStateButtons → linkButtons/sendEventButtons), but there's a small issue with your current mock setup—you're trying to mock individual function names as if they're separate modules, but all these functions are exported from the same ./bookingStates file. Let me help you fix that and build out proper test cases.

First, let's correct the mock approach. Since all functions come from the ./bookingStates module, we need to mock the entire module while specifying the behavior of each function we want to stub:

import { getBookingStateButtons, getBookingStateObject, linkButtons, sendEventButtons } from './bookingStates';

// Mock the entire bookingStates module
jest.mock('./bookingStates', () => ({
  __esModule: true, // Required if using ES modules
  getBookingStateButtons: jest.fn(),
  linkButtons: jest.fn(),
  sendEventButtons: jest.fn(),
  // Keep the real implementation of getBookingStateObject if we want to test it
  getBookingStateObject: jest.requireActual('./bookingStates').getBookingStateObject,
}));

Now let's write tests for each layer of your function chain:

Test that getBookingStateObject calls getBookingStateButtons #

This test verifies the top-level function correctly delegates to its dependency:

test('getBookingStateObject invokes getBookingStateButtons with the right parameters', () => {
  // Arrange: Prepare test data
  const mockBooking = { id: 'abc123', status: 'pending' };

  // Act: Call the function we're testing
  getBookingStateObject(mockBooking);

  // Assert: Verify the dependency was called correctly
  expect(getBookingStateButtons).toHaveBeenCalledTimes(1);
  expect(getBookingStateButtons).toHaveBeenCalledWith(mockBooking);
});

Test that getBookingStateButtons calls linkButtons and sendEventButtons #

This test checks that the middle layer function properly uses its two child functions:

test('getBookingStateButtons calls both linkButtons and sendEventButtons appropriately', () => {
  // Arrange: Set up mock data and return values
  const mockState = 'confirmed';
  const mockLinkBtns = [{ label: 'View Booking', url: '/bookings/abc123' }];
  const mockEventBtns = [{ label: 'Cancel', eventType: 'booking_cancel' }];

  linkButtons.mockReturnValue(mockLinkBtns);
  sendEventButtons.mockReturnValue(mockEventBtns);

  // Act: Call the function
  const result = getBookingStateButtons(mockState);

  // Assert: Verify dependencies were called, and result is correct
  expect(linkButtons).toHaveBeenCalledWith(mockState);
  expect(sendEventButtons).toHaveBeenCalledWith(mockState);
  expect(result).toEqual({
    linkButtons: mockLinkBtns,
    sendEventButtons: mockEventBtns
  });
});

• Isolate tests: Add jest.clearAllMocks() in a beforeEach block to reset mock call counts/arguments between tests, so one test doesn't pollute another.
• Mock selectively: Use jest.requireActual to keep real implementations of functions you want to test, while only mocking their dependencies.
• Validate return values: Don't just check if functions were called—verify they return the expected data too, to catch logic errors.

内容的提问来源于stack exchange，提问作者Sooraj