Jest test fails : TypeError: window.matchMedia is not a function

Question

This is my first front-end testing experience. In this project, I'm using Jest snapshot testing and got an error TypeError: window.matchMedia is not a function inside my component.

I go through Jest documentation, I found the "Manual mocks" section, but I have not any idea about how to do that yet.

Answer 1

The Jest documentation now has an "official" workaround:

Object.defineProperty(window, 'matchMedia', {
  writable: true,
  value: jest.fn().mockImplementation(query => ({
    matches: false,
    media: query,
    onchange: null,
    addListener: jest.fn(), // Deprecated
    removeListener: jest.fn(), // Deprecated
    addEventListener: jest.fn(),
    removeEventListener: jest.fn(),
    dispatchEvent: jest.fn(),
  })),
});

Mocking methods which are not implemented in JSDOM