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! If you have a module called math.js, you can mock it like this:

jest.mock('./math', () => ({
  add: jest.fn(() => 3),
}));

This will mock the add function to always return 3.

What if I want to mock a specific function from a module?

You can mock a specific function by using jest.spyOn(). For example:

import * as math from './math';
jest.spyOn(math, 'add').mockImplementation(() => 5);

This will mock the add function to return 5.

How do I reset the mocks after each test?

You can use jest.resetAllMocks() in the afterEach block to reset all mocks after each test.