Useful Testing Tools, Libraries and Frameworks For React Developers

We all know the love of developers for the most popular library, React. It's easy to learn, and it's easy to build the user interface of any website using React. If you're building an application, no matter what, you should test your application before serving it to the user. If you are a front-end developer working on the React library, you might have some favorite tool or framework for testing your React application. A lot of developers use Jest, Enzyme, or some other popular tools and libraries to test the components of React applications. However, every tool or framework is not the same for everyone. There are tons of testing frameworks and tools available in the open-source ecosystem for testing purposes of React applications.

Whether you're doing unit testing, integration testing, or end-to-end testing, choosing the right toolset and framework for testing is the key factor in leveraging TDD in React. In this blog, let's talk about some popular React testing frameworks and libraries that a lot of people use in their day-to-day jobs.

What is React?

React is a JavaScript library used to build user interfaces for websites and web applications. It helps developers create fast, interactive, and dynamic websites. Instead of reloading the whole page every time something changes, React updates only the parts that need to be changed. This makes websites feel faster and more responsive.

React is mainly used for building the frontend or the visible part of a website. It makes building complex user interfaces easier by breaking them into smaller, reusable pieces called components. These components can be buttons, forms, or even entire sections of a webpage.

Useful React Testing Tools

1. Jest

Jest is the most popular testing framework, with more than 16M downloads a week. It is created and maintained by Facebook. The team uses it to test all the JavaScript codes including React applications. It is also adopted by Airbnb, Uber, Intuit, and other teams as well. Jest comes with its test runner and assertion functions. This framework is also good for beginners who want to try incredibly fast JavaScript codes.

• Very fast performance. Airbnb saw a decrease in the total test runtime from 12 minutes to only 4.5 minutes when they switched from Mocha to Jest.
• It conduct snapshot, parallelization, and async method tests.
• Mock your functions, including third-party node_module libraries
• Possible to manage tests with larger objects using live snapshots.
• Standard syntax with report guide.
• Compatible with React, VueJS, Angular and many projects.

2. Mocha

Mocha is another popular test framework for Javascript developers. It provides browser support for NodeJS programs, asynchronous tests, test coverage reports, and the use of any claims library. It provides full control over how to test your code, with which tools, while you can plug in and out most supporting libraries and tools in your chain. Jest is the popular framework but it has some issues like mocking is confusing so Mocha is the alternative option in this case.

• Runs on Node.js and provides support for asynchronous front-end and back-end testing
• Helps in error tracking.
• Combination of Mocha with Enzyme and Chai is popular for the assertion, mocking, etc. Enzyme + Mocha is a good combination to test web applications written in ReactJS.

3. Chai

Chai is a popular assertion and expectations library for node and for the browser that can be paired with any javascript testing framework. An assertion is a way to declare what to expect in a test. Mocha doesn't come with assertion library built-in so a lot of developers pick Chai with Mocha for testing React application. Some functionality like expect, should, and assert helps you to declare what to expect in a test. It can be used to make assertions for functions, but also components later on by using Enzyme.

4. Jasmine

Jasmine is a great BDD open-source framework and test runner for testing all kinds of javascript applications. It includes both the visibility test and the response test of the user interface on several devices with different resolutions. A lot of developers who are Angular CLI users love to use Jasmine for testing the application. Developers mostly combine it with Babel and Enzyme to test React application. You can read about helper util library which is a designated to test the React application. Below is some pro side of the jasmine framework.

• A document object model (DOM) is not required for Jasmine.
• Helpful in both the front and back end tests.
• Async function tests.
• Mocking requests.
• Custom equality checker assertion.
• Custom matcher assertion.
• Solid documents and community support.

Keep in mind that Jasmine doesn't support snapshot tests, code coverage tools, parallelization (requires third-party tools), and native DOM manipulation (requires a third-party tool).

5. Enzyme

Enzyme is a testing utility designed to help developers for testing the React component without any hassle. Enzyme is one of the most used frameworks developed and maintained by Airbnb. Developers combine it with other frameworks such as Jest, Chai, or Mocha to test the React application. The enzyme is only used to render components, access things, find elements, interacting with elements, and simulate events. Chai or Jest can be used to make the assertions for it. You can test the outputs of React components, abstracting the rendering of components.

• Use shallow rendering.
• Access business implementations of your components.
• Conduct full DOM rendering.
• Use react-hooks in shallow rendering, with some limitations.

6. Cypress IO

Cypress is a very fast end to end testing framework that enables you to write your tests without any additional testing framework. It allows you to run your tests in the real browser or command line. Along with testing your code in the real browser, you can also use browser development tools side by side. The framework comes with its control panel that gives you control over the status of your tests. Some pros and advantages of using Cypress are

• Time travel with snapshots
• Screenshots and videos
• Automatic waiting
• Control network traffic without touching your server to test edge cases
• Built-in parallelization and load balancing makes debugging easier.
• Nice API to interact with page components.

7. React-testing-library

React-testing-library is created by Kent C. Dodds and supported by a vast community of developers. It allows you te to test the component easily and simulates the user behavior in your tests. Similar to enzyme this library is a complete set of React DOM testing utilities focused on imitating actual user actions and workflows. Read the article Revisiting React Testing in 2019 to make a choice in between react-testing-library and Enzyme. You can do the following things with react-testing-library

• Query your elements within text, label, displayValue, role, and testId
• Fire any event
• Wait for an element to appear with wait

There are some limitations of this library as well as you cannot conduct shallow rendering and you can not access the internal business of your components, such as states.

8. Puppeteer

Puppeteer is not a javascript framework, it is a headless Chromium Node library that provides API to control Chrome or Chromium through the DevTools protocol. You can start chromium and, with the provided API, navigate between pages, get buttons, and click on them. Puppeteer runs on an actual browser and it allows you to write end-to-end tests with an API similar to the browser. You can do many more things with Puppeteer such as generating screenshots, generating pre-rendered content from SPAs, automating actions like form submissions, keyboard inputs, etc. You can combine Puppeteer with Jest to test your React application end to end.

• Easy automated UI test, form submission, and keyboard input
• Easy creation of screenshots and PDF files of web pages
• Support for testing Chrome extensions.

Puppeteer doesn't support a large number of extensions, but the future is bright and promising.

Conclusion

We can see that each testing library and framework has its advantage and drawbacks. Whether it's a unit test, integration test, or end to end test, choosing the right tool helps a lot in getting the best result. To test the React components combining the right testing framework (e.g. Jest etc) with the right assertion/manipulation libraries (e.g. Enzyme etc) matters a lot for creating a smooth and flexible workflow, that can adapt while you upgrade, extend and modify your code.