React Testing Library Complete Guide

Among the various front-end development libraries, React is an important testing library and is frequently used by developers to build seamless and quality products. From enabling clear programming to being backed up by a strong community, this open-source JavaScript library helps deliver fast performance. However, these benefits of the software or applications are not only a result of better and clear programming.

Testing also plays an integral part in validating the quality of the product as well as its speed. Currently, numerous frameworks are used to test React components, such as Jest, Enzyme and React-Testing-Library. Though the former two are well renowned among testers, React Testing Library is steadily gaining momentum, due to the various benefits it offers to the testing team, and it is this method of testing React components that we are going to discuss in detail today, to further understand its significance.

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What is React Testing Library? (Click Here to Tweet)

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Introduced by Kent C. Dodds, React Testing-Library is a lightweight solution for testing React components and is commonly used in tandem with Jest. React Testing Library came into being as a replacement to Enzyme and is now encouraging better testing practices, by providing light utility functions on top of react-dom and react-dom test-utils. It is an extremely beneficial testing library that enables testers to create a simple and complete test harness for React hooks as well as to easily refactor code going forward.

The main objective of this library is to provide a testing experience that is similar to natively using a particular hook from within a real component. Moreover, it enables testers to focus directly on using the library to test the components and assert the results. In short, React Testing Library guides testers to think more about React testing best practices, like selectors and accessibility rather than coding. Another reason that makes it helpful is that this library works with specific element labels of the React component and not the composition of the UI.

Want to get a better insight into the working of React Testing Library? Check out the React Testing Library examples here.

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Key Points of React Testing Library:

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From supporting new features of React to performing tests that are more focused on user behavior, there are numerous features of React Testing Library that make it more suitable for testing React components than others.

Some of these features are:

• It takes away excessive work required to test React components well.
• It is backed up as well as recommended by the React community.
• It is not React specific and can be used with Angular and other languages.
• It enables testers to write quality tests that ensure complete accuracy.
• Encourages applications to be more accessible.
• It offers a way to find elements by a data-testid for elements where the text content and label don't make sense.
• Avoids testing the internal component state.
• Tests how a component renders.

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The Guiding Principles of React Testing Library:

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The guiding principle of this library is the more the tests resemble the way the software is used the more confidence they can give the testing team. To ensure this, the tests written in React Testing Library closely depict the way users use the application. Other guiding principles for this testing library are:

• It deals with DOM nodes rather than component instances.
• Generally useful for testing individual React components or full React applications.
• While this library is focused on react-dom, utilities are included even if they don't directly relate to react-dom.
• Utility implementations and APIs should be simple and flexible.

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Why React Testing Library is required?

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React Testing Library is an extremely beneficial testing library and is needed when the team of testers wants to write maintainable tests for React components, as well as when there is a need to create a test base that functions uniformly even when refactors of the components are implemented or new changes are introduced. However, the use of the React Testing Library is not limited to this. As this library is neither a test runner or framework nor is it specific to a testing framework, it is also used in the following two circumstances:

• In cases when the tester is writing a library with one or more hooks that are not directly tied to a component.
• Or when they have a complex hook that is difficult to test through component interactions.

Tests Performed While Testing React Components:

There are various tests for your React component or React application testing that ensures that they deliver the expected performance. Among these, the following are the most crucial tests performed by the team and are hence discussed in detail:

• Unit Testing:
  An integral part of testing React components, unit testing is used to test the isolated part of the React application, usually done in combination with shallow rendering as well as functional testing React components. This is further executed with the assistance of an important technique of front-end unit testing react component, snapshot testing.
  • Snapshot Tests:Another testing technique used to test React components in React Testing Library snapshot testing, wherein the team takes a snapshot of a React component and compares it with later versions to validate that it is bug-free, runs accurately and depicts expected user experience. The main objective of Snapshot testing is to make sure the layout of the component didn't break when a change was implemented.

    Snapshot testing is suitable for React component testing as it allows the testing team to view the DOM output and create a snapshot at the time of the run. Moreover, this testing technique is not limited to testing implementation details or React testing library hooks and is used with other testing libraries and frameworks, like Jest, as it enables testing of JavaScript objects.

• Integration Tests:
  One of the most important tests performed to test React components, Integration Testing, ensures that the composition of the React components results in the desired user experience. Since writing React apps is all about composing components, Unit Testing React with Jest alone is not suitable for ensuring that the app, as well as the components, are bug-free. Integration tests validate whether different components of the app work or integrate with each other by testing individual units by combining and grouping them.
• End-to-End Testing:
  Performed by combining testing library React and Cypress or any other library or frameworks, end-to-end testing is another important step of the testing activities. It helps ensure that the React app works accurately and delivers the necessary functionality expected by the users. This test is a multi-step that combines multiple units and integrates the tests into one huge test.

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Other Important Tools & Libraries:

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Though React-Testing-Library is a prominent library for testing React components, it is not the only library out there. There are various other React testing tools and libraries used by the team of testers to verify the quality and accuracy of React components. A few of these are mentioned below:

1. Jest: Adopted by large scale organizations like Uber and Airbnb, Jest is among the most popular frameworks and used by Facebook to test React components. It is also recommended by the React team, as its UI snapshot testing and complete API philosophy combines well with React.
2. Mocha: One of the most flexible Javascript testing libraries, Mocha, just like Jest and other frameworks can be combined with Enzyme and Chai for assertion, mocking, etc. when used to test React. It is extremely configurable and offers developers complete control over how they wish to test their code.
3. Chai: Another important library used for testing components, Chai is a Behavior Driven and Test Driven Development assertion library that can be paired with a JavaScript testing framework.
4. Karma: Though not a testing framework or assertion library, Karma can be used to execute JavaScript code in multiple real browsers. It is a test runner that launches an HTTP server and generates HTML files. Moreover, it helps search for test files, processes them and runs assertions.
5. Jasmine: A Behavior Driven Development (BDD) testing framework used for JavaScript tests, Jasmine, is used to test the React app or components. It does not rely on browsers, DOM, or any JavaScript framework and is traditionally used in various frameworks like Angular. That's not all, Jasmine consists of a designated help util library that is built to make the testing workflow smoother.
6. Enzyme: One of the most common frameworks usually discussed along with React Testing Enzyme is not a testing framework, but rather a testing Utility for React that enables testers to easily test outputs of components, abstracting the rendered component. Moreover, it allows the team to manipulate, traverse, and in some cases stimulate runtime. In short, it can help the team React test render components, find elements, and interact with them.
7. React Test Utils and Test Renderer: Another collection of useful utilities in React, React test renderer is used in identifying and throwing an error using any testing library Jest Dom for example. React-test-renderer typescript enables the team to render React components into pure JavaScript objects without depending on DOM. It can support the basic functionality needed for testing React components and offers advantages that it is in the same repository as the main React package and can work with its latest versions.
8. Cypress IO: A JavaScript end-to-end testing framework, Cypress is easy to set-up, write, and debug tests in the browser. It is an extremely useful framework that enables teams to perform end-to-end React application testing, while simultaneously making the process easy. It has a built-in parallelization and load balancing, which makes debugging tests in CI easier too.

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Conclusion:

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Testing, be it for a React component, application or software, is crucial to validate the quality, functionality, as well as UX & UI. React Testing Library is among the various testing frameworks that are helping testers create apps that are suitable for users worldwide. From remarkable React testing library accessibility to a scalable React test environment, label text features, and more, this front-end testing framework offers a wide range of advantages, which is making it popular among testers. So, whether you are using the Jest test function or React testing library, testing React components and applications is easier with all.

Want to understand the scope of React Acceptance Testing? Click here.