10 React Testing Best Practices

React is a JavaScript library for building user interfaces. It is declarative, efficient, and flexible. React is used by Facebook, Instagram, Netflix, and many other companies.

React is a popular choice for front-end development because of its virtual DOM, which makes it easy to create fast and responsive user interfaces. However, one of the challenges of working with React is that it can be difficult to test React components.

In this article, we will discuss 10 React testing best practices that will help you write better tests for your React components.

1. Use the Right Testing Library

React testing libraries are designed to test React components, and they provide a number of features that make this possible. For example, they allow you to render a React component in a “test” environment and make assertions about its output. They also provide methods for simulating events so that you can test how your component responds to user input.

There are a few different options when it comes to choosing a React testing library, but the most popular ones are Enzyme and React Testing Library. Enzyme is a library created by Airbnb, and React Testing Library is a library created by Facebook.

Both Enzyme and React Testing Library are widely used and well-supported, so which one you choose is mostly a matter of personal preference. However, there are a few key differences between them that you should be aware of.

Enzyme focuses on providing a comprehensive API for making assertions about the output of a React component. This means that it has a lot of methods for inspecting the rendered HTML, and it also provides a way to directly access the underlying React component instance.

React Testing Library, on the other hand, takes a more “black box” approach. It doesn’t provide any methods for directly inspecting the output of a React component. Instead, it encourages you to write tests that focus on the behavior of your component, rather than its implementation details.

So, which one should you use? If you’re just getting started with React testing, React Testing Library is a good option. It’s simpler to use, and it will help you get into the habit of writing tests that focus on behavior rather than implementation.

Once you’re more comfortable with React testing, you can experiment with Enzyme to see if it’s a better fit for your needs.

2. Test at Different Levels of Abstraction

If you only test your React components at the unit level, you’re only testing the functionality of those individual units. This is important, but it’s not the whole story. You also need to make sure that those units work together correctly when they’re integrated. That’s where integration tests come in.

Integration tests are higher-level tests that exercise a group of components together. They’re closer to what the user will actually see and interact with. As such, they’re better at finding bugs that only occur when multiple components are used together.

It’s important to have both unit tests and integration tests for your React components. Unit tests give you confidence that the individual units are working correctly, while integration tests give you confidence that the units work correctly when they’re used together.

3. Write Tests for Components and Their Behaviors, Not Implementation Details

This means that if you change the way a component is implemented, but its behavior stays the same, your tests should still pass. For example, if you change the way a component renders its children from an array to a map, your tests should not need to be updated.

One way to achieve this is by using shallow rendering, which allows you to test a component in isolation from its children. This ensures that your tests are only testing the component itself, and not its implementation details.

Shallow rendering is also useful for performance reasons, as it can be much faster than rendering the full component tree.

4. Don’t Mock What You Don’t Own

Mocking is a great way to isolate the component you’re testing from its dependencies. However, if you mock something that you don’t own, you’re more likely to write a test that doesn’t reflect how the component actually works in production.

For example, let’s say you’re testing a component that renders a list of items. The component gets the items from an API. You could mock the API call so that the component always gets the same data, but then you’re not testing how the component behaves when the API call fails or returns different data.

It’s better to use a real API in your tests so that you can test all the different ways the component can behave. Of course, you don’t want to make actual API calls in your unit tests because they’ll be slow and unreliable. That’s why it’s important to use a mocking library like React Testing Library that lets you mock the API calls without changing the way the component behaves.

5. Avoid Snapshot Testing

Snapshot testing is a great way to catch visual regressions, but it’s not so great at catching logic errors. A snapshot test will only tell you that something has changed, not why it has changed.

This means that if there’s a bug in your code, a snapshot test will likely not catch it. Instead, you should focus on writing unit tests that test the individual pieces of your code. That way, if there’s a bug, you’ll know exactly which piece of code is causing the problem.

Snapshot testing can also be slow and brittle. If you make a change to your code that doesn’t affect the rendered output, the snapshot will still fail. This can be frustrating for developers who are trying to make small changes.

Overall, snapshot testing is a useful tool, but it should not be the only tool in your React testing arsenal.

6. Keep Your Tests Fast

Slow tests give you less feedback, so you’re more likely to miss bugs. They also make it harder to refactor your code, since you have to wait longer for the feedback loop. And they make it harder to run your tests often, which means you’re more likely to miss bugs that only happen in certain conditions.

There are a few ways to keep your React tests fast. One is to use shallow rendering, which renders a component without its children. This can make your tests run faster because you don’t have to render all the child components.

You can also use mock functions to stub out behavior that would otherwise make your tests slow. For example, if you’re making an API call in your component, you can use a mock function to stub out that behavior. That way, your test doesn’t have to actually make the API call, which can make it run faster.

Finally, you can run your tests in parallel. This means running multiple tests at the same time, which can speed up your overall test suite.

7. Make Sure to Clean Up After Yourself

When you’re working with React, every time you create a new component, that component is going to have its own set of tests. And if you don’t clean up after yourself, those tests are going to pile up and eventually become unmanageable.

What’s more, if you’re constantly adding new tests without cleaning up the old ones, eventually your test suite is going to get so big that it’s going to slow down your development process. So it’s important to take the time to delete old tests that are no longer relevant, and to refactor your existing tests so that they’re more concise and easier to understand.

Doing this will not only make your life easier in the long run, but it’ll also make it easier for other developers who have to work with your code.

8. Consider Using React Testing Library

React Testing Library is a set of helpers that let you test React components without relying on their implementation details. This is important because it lets you keep your tests up-to-date as your code changes, and it also reduces the amount of mocking you have to do.

React Testing Library is also lightweight and easy to use. It’s been designed specifically for testing React components, so it doesn’t include any unnecessary functionality.

If you’re looking for a comprehensive guide to React testing, check out this course from TestDriven.io.

9. Be Mindful of Accessibility

React is a JavaScript library used to create user interfaces. When building React applications, developers have the opportunity to create amazing experiences for users with disabilities. However, if accessibility is not considered during the development process, it’s easy to create an inaccessible React application.

There are many ways to test for accessibility, but one simple way to get started is to use the React Testing Library. This library provides a set of helper functions that make it easier to assert whether a given React component is accessible or not.

To learn more about accessibility and React, check out the following resources:

– The A11y Project
– React Accessibility Guide
– Deque University

10. Learn from Others

When you’re just starting out, it’s easy to get overwhelmed by all of the different testing options and configurations. By following along with someone who is more experienced, you can learn what works and what doesn’t without having to go through all of the trial and error yourself.

Additionally, seeing how others write their tests can give you some insight into how they think about testing React components. This can help you better understand how to approach testing your own components.

Finally, when you’re stuck on a particular issue, it can be helpful to see how someone else has tackled it. Oftentimes, there is more than one way to skin a cat, and seeing how others have solved similar problems can give you some ideas for how to solve yours.