Mastering React Test-Driven Development

Pulling out generator functions for reducer actions

The reducer tests we just wrote contain a lot of repetition. In fact, the majority of reducers will follow exactly the same pattern: each action will set some new data, and ensure that the existing state is not lost.

Let's write a couple of test generator functions to do that for us, to help us dry up our tests:

1. Create a new file, test/reducerGenerators.js, and add the following function:

export const itMaintainsExistingState = (reducer, action) => {  it('maintains existing state', () => {    const existing = { a: 123 };    expect(reducer(existing, action)).toMatchObject(existing);  });};

2. Add the following import to the top of src/sagas/customer.test.js:

import { itMaintainsExistingState } from ...