Mastering React Test-Driven Development

Writing the reducer

We'll start, as ever, with the reducer:

1. Create a new file named test/reducers/environment.test.js and add the following describe block. This covers the basic case of the reducer needing to return the default state when undefined is passed to it:

import {  environmentReducer as reducer} from '../../src/reducers/environment';describe('environmentReducer', () => {  it('returns default state when existing state is undefined', () => {    expect(reducer(undefined, {})).toEqual({      promptFocusRequest: false    });  });});

2. Make the test pass with the following code. This isn't technically the simplest code that will make this work, but it is the simplest thing if you consider the changes that would have to be made later if we didn't go ...