总结三种常见的Jest Mock方法：

1. Mock a method of module in test

// App.test.js
// 1. Import module
import api from '../../api'  

// 2. Mock method
jest.mock('../../api', () => ({  
  getUser: jest.fn(),
}));

describe('App', () => {
  test('Mock a method', async () => {
    // 3. Return value
    api.getUser.mockReturnValue(Promise.resolve(1010));
    ......
  });
});

2. Mock constants variable

// constants.js 
export const subject = {
    name: '',
    teacher: '',
}

// App.js
import { subject } from "./constants";

const App = () => {
  ...
  const [subject, setSubject] = useState(subject);
  ...
}

export default App;

// App.test.js
// 1. Import file
import * as constants from './constants';

// 2. Override the variable object
Object.defineProperty(constants, 'subject', {
      value: {
          name: 'math',
          teacher: 'A',
      },
      writable: true
});

 // 3. Test conponment
 it('test', () => {
     wrapper = render(<App />);  
     ...
  });

3. Mock a hook method

// App.js
import {useToast} from "@moudle";

const App = () => {
  ...
  const add = useToast()
  add({message: 'test'})
  ...
}

export default App;

// App.test.js
// 1. MockAddToast
const mockAddToast = jest.fn();

jest.mock('@moudle"', () => ({
    ...jest.requireActual('@moudle"'),
    useToast: () => mockAddToast,
}));

 // 2. Test conponment
 it('test', () => {
     render(<App />); 
     expect(mockAddToast).toHaveBeenCalledTimes(1) 
     ...
  });

References

• Mocking-hooks-for-testing-with-jest-and-react-testing-library