Test-Driven Development (TDD) with React/Nextjs

#react #tdd #typescript #reactjsdevelopment

Test-driven development (TDD) with a React frontend that uses libraries like react-query, react-table, Tailwind CSS, and Mock Service Worker (MSW) involves writing tests that assert the behavior of your application. Here are some areas you might consider when writing your tests:

Components:

Use Jest/vitest and React Testing Library for testing components. Assert that components render correctly based on different props.
With react-table, test that your table components render the expected data and support the necessary interactions, such as sorting or filtering.
API Interactions:

With react-query, you can test your query and mutation functions to ensure they behave as expected. This includes how your app reacts to success, error, and loading states.
MSW allows you to create a mock server in the browser. Use this to simulate API responses and errors for your tests, ensuring your app behaves correctly given different server responses.
Styling and Layout:

With Tailwind, since the focus is more on utility classes and less on custom styles, it's less likely that you need to write specific tests for styles.
You can still perform visual regression testing using tools like Cypress, Jest Snapshot, or Storybook to ensure your UI does not change unexpectedly.
You can also use accessibility testing tools to ensure your site is accessible, which is particularly important if you are heavily customizing the styles.
Integration and End-to-End tests:

Once you have the individual units of your app tested, write some integration tests to make sure they work well together.
Tools like Cypress or Puppeteer/Playwright can be used to automate browser-based interactions, testing flows that involve several components.
Simulate user interactions like button clicks, form submissions, etc., and check if the app behaves as expected.
Edge Cases and Error Handling:

Make sure you have tests for any edge cases you can think of.
It's especially important to test your error handling to ensure your app can recover gracefully from errors.

Remember, TDD is about writing your tests first and then writing the code to make those tests pass. So you would first write tests for a small piece of functionality, run the tests to make sure they fail, then write the code to make them pass, and finally refactor the code while keeping the tests green. This cycle is often referred to as Red-Green-Refactor.