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React is a popular JavaScript library for building user interfaces. It is known for its sizzling performance, extraordinary flexibility, and a large community of developers. However, testing React applications can be challenging as they are often nested, complex, state-driven, and rendered dynamically.
Despite these challenges, there are several React testing libraries and techniques that can help developers and testers to make testing easier. Therefore for them, it's crucial to keep up with the latest trends, updates, and improvements in React testing libraries in 2023.
In this blog, we will provide an overview of the top React testing libraries of 2023 along with the latest updates and improvements. Here we will cover popular options such as Chai, Jest, Mocha, Karma, Jasmine, Enzyme, React-Testing-Library, and more.
So, let’s get started! But before that understand the importance of React app testing.
React testing is essential for the following reasons:
Testing ensures the quality of your React app by identifying and preventing bugs, errors, and regressions.
Rigorous testing improves the reliability and stability of React components, verifying that they behave as expected in various scenarios.
Tests promote modular and maintainable code, acting as documentation for expected component behavior.
Testing detects unintended changes or breaks in existing functionality caused by new code, preventing regressions.
Tests provide confidence when refactoring or making significant changes to the codebase.
Tests foster collaboration and enable developers to work efficiently with a shared understanding of expected behavior.
Automated testing is crucial in the CI/CD pipeline, catching issues early and streamlining the release process.
Overall, React testing ensures software quality, enhances reliability, promotes maintainability, prevents regressions, supports refactoring, facilitates collaboration, and enables efficient development workflows.
The year 2023 brings exciting updates and improvements to React testing libraries. These libraries are essential for testing React components and guaranteeing the quality and functionality of your React applications. Let's explore some of the popular libraries along with the latest features and updates and how they can elevate your React testing workflows.
Jest is the most popular testing framework created and maintained by Facebook and is highly recommended by the React Community. The library is used to test React components and is used by popular apps like Uber, Airbnb, and other big companies.
The framework comes with its own test runner and assertion functions. It can work with Babel, TypeScript, Node, React, Angular, Vue, and other technologies.
Jest 29.5 has changed the default snapshot formatting to {escapeString: false, printBasicPrototype: false}. If you want to keep the old behavior, you can set the snapshotFormat property to: {escapeString: true, printBasicPrototype: true}.
Also, the Snapshot testing has been improved by adding the ability to take snapshots of multiple components in a single test. This makes it easier to test complex applications.
The Jest version supports Node.js versions 14.15, 16.10, 18.0, and above.
Mocking has been improved by adding the ability to mock functions that are defined in other files. This makes it easier to test code that depends on external libraries.
The Coverage reporting has been improved by adding the ability to report coverage for individual components. This makes it easier to track the coverage of your tests.
Performance has been improved by reducing the number of times that Jest renders components. This makes Jest faster and more efficient.
Jest 29.5 has added new features such as support for asynchronous testing and parameterized tests. This makes it easier to test React applications in a variety of scenarios.
Enzyme is another popular testing tool built by Airbnb designed to help developers test the React components with ease. It can be combined with testing tools such as Jest, Mocha, and Jasmine for testing React applications.
The testing utility can simplify assertion, manipulation, and traversal of your React component’s output. Enzyme API is highly intuitive, flexible, and compatible with all major test runners.
Enzyme 4.0.0 now supports React 18, the latest version of React. This means that you can use Enzyme to test React applications that are built with React 18.
Enzyme 4.0.0 introduces two new APIs for mounting React components: shallowMount and mount. These APIs are designed to be more flexible and easier to use than the previous mount API
The library now provides better support for functional components. This includes the ability to access the props and state of functional components, as well as the ability to simulate user interaction with functional components.
The library introduces a new API for interacting with the DOM. The API is designed to be more consistent with the DOM APIs that are provided by React
The new version includes some bug fixes for a number of edge cases; this has improved the stability and Reliability of the Enzyme library.
Know more about using Jest and Enzyme in your React application.
Mocha, a JavaScript testing framework, is compatible with both Node.js and web browsers. It simplifies the process of asynchronous testing. Mocha executes tests sequentially, providing flexibility and precise reporting. It also accurately associates uncaught exceptions with their respective test cases.
Latest version Mocha 10.2: Updates and Improvements
The enhancement adds the ability to decorate ESM-module names right before they will be imported by passing the esmDecorator function to loadFilesAsync method.
1 mocha.loadFilesAsync({ 2 esmDecorator: file => `${file}?foo=bar`}) 3
Due to the wrong variable being referenced in #mocha .test.fail::before, the failed test icon (✖) is currently incorrectly colored as #00d6b2 instead of #cc0000 (light schema) or #ff4444 (dark schema). Ref example.
Chai React is a JavaScript assertion library for Node and browser that can be paired with any JavaScript testing framework. The latest version of Chai is 4.3.7, which was released on March 7, 2023. This version includes a number of new features and bug fixes.
The deep-eql package was updated to support the comparison of symbols. This means that Chai can now compare objects that contain symbols, which was not possible in previous versions of Chai.
This package now uses ESM modules CommonJS environments are no longer supported. If you wish to use a CommonJS environment, please continue to use Chai 4.
NodeJS < 16: If you are using NodeJS v4-v15, please continue to use Chai 4.
Internet Explorer 10 and 11: The support is dropped for Internet Explorer 10 & 11.
Safari version < 14: If you wish to test against Safari v10-v13 please continue to use Chai 4.
EdgeHTML < 18: If you wish to test against Edges older than 18, please continue to use Chai 4.
Firefox version < 102: If you wish to test against Firefox 60 through to 101 please continue to use Chai 4
Chrome version < 108: If you wish to test against Chrome 68 through 107 please continue to use Chai 4.
The testing library provides a productive testing environment to developers, where they don’t have to set up loads of configurations. Here, developers can simply write code and get instant feedback from their tests.
In Karma, version 6.4, support for SRI verification was added for both link tags and script tags. This means that you can now use Karma to verify the integrity of the resources that are loaded by your tests.
To use SRI verification in Karma, you need to add the integrity attribute to the link or script tag. The integrity attribute should contain the hash of the resource that you want to verify. For example, the following code would verify the integrity of a JavaScript file called my-script.js:
1 <script src="my-script.js" integrity="sha256-1234567890abcdef" /> 2
If the hash of the resource that is actually loaded does not match the hash that is specified in the integrity attribute, then Karma will fail the test. This will help to ensure that the resource has not been tampered with since it was published.
React Testing Library is a lightweight testing library for React. It provides a number of utilities that make it easy to test React components without having to mock out the DOM or other parts of the React ecosystem.
React Testing Library is agnostic to the testing framework that you use. This means that you can use it with any testing framework, such as Jest, Mocha, or Karma.
The latest version of React Testing Library is 12.2.3, which was released on March 8, 2023. This version includes a number of new features and bug fixes.
Prevent "missing act" warning for queued microtasks.
The @testing-library/dom package has been updated to version 9.0.0. This package provides a number of utilities for testing the DOM, and the update includes a number of new features and bug fixes. Also, the latest version drops support for Node.js version 12.x.
Jasmine is the unit testing tool for JavaScript. It is a BDD framework that provides a suite of matchers for making assertions about the code being tested. It does not require DOM and has a clean, obvious syntax that makes it easy to write tests.
Support for parallel execution in Node via the Jasmine package. Added Node 20 to supported environments.
It is the next-generation front-end testing tool built for modern web applications. The tool helps you to:
Set up tests, Write tests, Run tests, and Debug Tests. The tool is often compared to Selenium. However, it is fundamentally and architecturally different from it.
The tool is popular among QA engineers building web applications with modern JavaScript frameworks. It allows you to write:
A new Debug page has been added to make it easier to debug failed CI test runs recorded to the Cypress Cloud from your local Cypress app.
Cypress now supports running tests with Chrome's new --headless=new flag. This flag allows you to run Cypress tests in a headless mode that matches the headed browser implementation.
Cypress can now test pages with targeted CSP headers by specifying the allow list via the experimentalCspAllowList configuration option.
Improved video compression:
The video compression configuration option now accepts both a boolean or a Constant Rate Factor (CRF) number between 1 and 51. This allows you to control the quality of the video recordings that are generated by Cypress.
In addition to these major updates, there have also been several smaller improvements and bug fixes in Cypress version 12.5 and above. For a complete list of changes, please refer to the Cypress changelog.
Puppeteer is a Node.js library that offers a convenient interface for managing Chrome/Chromium using the DevTools Protocol. By default, Puppeteer operates in headless mode, but it can be customized to run in the full Chrome/Chromium interface, commonly referred to as "headful" mode.
The things that can be done manually in the browser can be done using Puppeteer. Such as,
The feat(screenshot): enable the optimizeForSpeed feature in Puppeteer version 20.8 allows you to take screenshots more quickly by disabling certain features that are not essential for taking a screenshot. This can be useful if you are taking screenshots of pages that are very large or complex.
To enable this feature, you can pass the optimizeForSpeed option to the takeScreenshot() method.
The fix: add an internal page.locatorRace change in Puppeteer version 20.8 addresses a race condition that could occur when multiple requests were made to the page.locator() method. This race condition could cause the wrong element to be returned, which could lead to errors in your code.
The fix for this issue involves adding an internal page.locatorRace method that is used to synchronize access to the page.locator() method. This ensures that only one request is made to the page.locator() method at a time, which prevents the race condition from occurring.
Vitest is a unit testing framework built on Vite with an eye for speed and minimal config. It is designed to be faster and more efficient than Jest, while still providing a familiar API. Vitest is also compatible with Jest's ecosystem, so you can easily migrate your existing tests.
Here are some of the features of Vitest:
Though Vitest is a relatively new testing framework, it is gaining popularity due to its speed and efficiency. If you are looking for a fast and easy-to-use unit testing framework, Vitest is a good option.
Vitest version 0.32.0 changed the default include globs to be compatible with Jest.
This fix adds SubmitEvent, DOMRectReadOnly, and DOMRect to the JSDom living keys so that they are available in tests when running in the JSDom environment.
Besides the above libraries and tools, React provides React Test Utils and Test Renders that helps you to simplify React testing within your loved testing framework.
ReactTestUtils simplify the process of testing React components within your preferred testing framework. At Facebook, Jest is our preferred testing framework for seamless JavaScript testing. You can explore the React Tutorial on the Jest website to learn how to begin using Jest.
The provided package offers a React renderer that enables rendering React components to plain JavaScript objects, independent of the DOM or native mobile environments. In essence, this package simplifies the process of capturing a snapshot of the platform view hierarchy, resembling a DOM tree, generated by a React DOM or React Native component, without relying on a browser or Jsdom.
In the article, we have discussed the top 10 React testing libraries and tools along with their latest versions- Features, improvements, and bug fixes. Staying up-to-date with these React testing libraries helps you to ensure efficient and effective testing of React applications.
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