How do I mock modules in Jest?

How do I mock modules in Jest?

You can mock modules in Jest using jest.mock() function. This allows you to replace the actual module with a mock implementation.

Can you show me an example of mocking a module?

Sure! Here's a simple example:

// myModule.js
export const fetchData = () => {
  return 'real data';
};

// myModule.test.js
import { fetchData } from './myModule';

jest.mock('./myModule', () => ({
  fetchData: jest.fn(() => 'mocked data'),
}));

test('fetchData returns mocked data', () => {
  expect(fetchData()).toBe('mocked data');
});

What if I want to restore the original implementation?

You can use jest.restoreAllMocks() to restore the original implementations of all mocked modules after your tests.

Are there any best practices for mocking in Jest?

Yes! Some best practices include mocking only what you need, keeping mocks close to the tests, and using clear naming conventions for your mocks.