Module Mocks

Jest · Reference cheat sheet

📋 Overview

Automock modules with jest.mock, manual __mocks__ folders, and virtual mocks. Control Node built-ins and CSS/assets via mappers.

Factories run in a sandboxed scope; hoist rules apply to jest.mock.

Manual mock:

src/
  api.js
  __mocks__/
    api.js

// __mocks__/api.js
export const getUser = jest.fn();

jest.mock('./api');
import { getUser } from './api';
getUser.mockResolvedValue({ id: 1 });

Virtual mock:

jest.mock('analytics', () => ({ track: jest.fn() }), { virtual: true });

Asset mapper:

moduleNameMapper: {
  '\\.svg$': '<rootDir>/test/svgrMock.js',
  '\\.(css)$': 'identity-obj-proxy',
},

Unmock / isolate:

jest.unmock('./api');
jest.isolateModules(() => {
  const mod = require('./fresh');
});