How do test async components with Jest?

Question

can anyone tell me how to wait in jest for a mocked promise to resolve when mounting a component that calls componendDidMount()?

class Something         


        

Answer 1

Jest has mocks to fake time travelling, to use it in your case, I guess you can change your code in the following style:

import { API } from 'api';
import { API as mockAPI } from '__mocks/api';

API.get = jest.fn().mockImplementation(mockAPI.get);

jest.useFakeTimers(); // this statement makes sure you use fake timers

describe('Something Component', () => {
  it('renders after data loads', () => {
    const wrapper = mount(<Something />);

    // skip forward to a certain time
    jest.runTimersToTime(1);

    expect(mountToJson(wrapper)).toMatchSnapshot();
  });
});

Alternatively to jest.runTimersToTime() you could also use jest.runAllTimers()