We will now test the App component of our application. As this is not a connected component the spec for the App will simply a single snapshot test.

Create the __specs__ directory inside of app/js/components/App/ and add the file App.spec.jsx.

We will then simply import shallow, the App component, and write a test expecting the mounted component to match the Jest snapshot.

// app/js/components/App/__specs__/App.spec.jsx

import React from 'react';
import { shallow } from 'enzyme';

import App from '../';

describe('App', () => {
  it('matches the snapshot', () => {
    const wrapper = shallow(<App />);

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

That's all we have to do. Make sure to run the tests and ensure they are passing and that the snapshot is written before continuing to the next step.