react-hooks-testing-library VS redux-mock-store

While generally it's recommended to test the component using the hooks rather than the hooks themselves, sometimes you might find it necessary to test custom hooks directly. For such cases, there's React Hooks Testing Library. This library allows you to create a simple test harness for React hooks that handles running them within the body of a function component, as well as updating and unmounting them.

To do so, we can install and use Render hooks from React Testing Library:

Of course, you could isolate the logic inside a hook, and there's an awesome way of testing it with renderHook. But yet, you're trapped into react features, if they change their API, you will have to put your hands in your working logic and adapt some stuffs to keep up to date.

Relocating functions to a custom hook makes them accessible for testing (plus you’re keeping business logic separate from the UI, in accordance with best practices). There’s even a library to help with testing custom hooks: react-hooks-testing-library.

testing-library provides one more library exactly for such purpose allowing us to avoid headache and safe strength for actual testing. It is called @testing-library/react-hooks

Next, we need to install react-hooks-testing-library package. It's a simple testing utility that allows testing hooks with ease. You can read more about this package here.

As for hooks, there's https://react-hooks-testing-library.com/

Use @testing-library/reacthooks

Now I don't need to worry about React lifecycle methods. I can test my hook if I want to, but it hardly seems worth it here. If I would, it would be easier to do so using react-hooks-testing-library

To fix this, the simple way is to mock a redux store. I need to install redux-mock-store and its typing:

For a long time I relied on redux mock store to preload data into my components for rendering during tests. This approach makes it easy to take a snapshot of a component with arbitrary data and ensure that it renders correctly. Where it completely fails is testing interactions.

Redux Toolkit includes a configureStore method that allows you to preload it with state. The createStore method in redux includes this option as well. In the old days I would rely on tools like redux mock store to generate redux stores for testing, but you don't need it. You can generate a store for your tests that includes exactly the same reducers as your app, but also comes pre-loaded with whatever state you need for your tests.

The above example checks the actions executed by someThunkFunction. The mockStore function used in the example comes from the redux-mock-store library.