Using jest.fn() for custom mocking

jestfn-for-custom-mocking.js

describe('Using jest.fn() for Custom Mocking', () => {
  let mockAxiosGet;

  beforeEach(() => {
    mockAxiosGet = jest.fn(); // Create a custom mock function
    axios.get = mockAxiosGet; // Override axios.get with the mock function
  });

  afterEach(() => {
    jest.restoreAllMocks();
  });

  it('mocks API with custom jest.fn()', async () => {
    const data = { name: 'Jane Doe' };
    mockAxiosGet.mockResolvedValueOnce({ data });

    const result = await fetchData('https://api.example.com/user/1');
    expect(result).toEqual(data);
    expect(mockAxiosGet).toHaveBeenCalledWith('https://api.example.com/user/1');
  });

  it('mocks API with multiple jest.fn() calls', async () => {
    const firstResponse = { name: 'John Doe' };
    const secondResponse = { name: 'Jane Doe' };

    mockAxiosGet
      .mockResolvedValueOnce({ data: firstResponse })
      .mockResolvedValueOnce({ data: secondResponse });

    const firstResult = await fetchData('https://api.example.com/user/1');
    const secondResult = await fetchData('https://api.example.com/user/2');

    expect(firstResult).toEqual(firstResponse);
    expect(secondResult).toEqual(secondResponse);
    expect(mockAxiosGet).toHaveBeenCalledTimes(2);
  });
});