context-async-test.js

import { mount } from 'enzyme';

import { PhotosContextInner } from './PhotosContext';

describe('PhotosContext', () => {
  test('fetchPhotos', async () => {
    const api = {
      fetchPhotos: () => ({ data: [{ caption: 'photo caption', src: 'src' }] }),
    };

    const wrapper = mount(<PhotosContextInner api={api} />);

    expect(wrapper.state()).toMatchSnapshot();
    await wrapper.instance().fetchPhotos();
    expect(wrapper.state()).toMatchSnapshot();
  });
});