10 Useful Jest Libraries and Extensions for Java Developers

10 Useful Jest Libraries and Extensions for Java Developers

Testing any application enables developers to ensure that everything is functioning as intended and that they are going to offer a flawless user experience. Application testing allows developers to check whether their application complies with UI, performance, and functional requirements.  Various techniques can be used to evaluate web-based apps. Many open-source developers have merged these testing techniques into reusable libraries.

Many testing frameworks and libraries in the open-source community can be used for testing. One such well-liked and simple-to-use library among Java developers is Jest. No matter how complex the web application is, developers can develop its user interface with Jest. Several libraries are available for testing the Jest application. The top 10 Jest testing libraries and extensions for Java developers are highlighted in this post to help developers with testing. However, let’s first define Jest and discuss its features before moving on.

Jest Framework

Jest is an open-source JavaScript testing framework developed by Facebook primarily for testing React-based apps. Its primary purpose is to maintain the accuracy of everything created using JavaScript, whether it is mobile applications or browser rendering of web applications. It enables the creation of tests using a user-friendly, recognizable, and feature-rich API that provides immediate feedback for the written code.

Developers gain access to an excellent toolset through Jest, which is centrally located, well-maintained, well-organized, and flexible to meet the needs of developers. Another superb feature is that much of its functionality is not dependent on third-party tools.

Both front-end and back-end application testing have significantly benefited from the popularity of Jest, which makes testing delightful. Its many additional features, such as a test runner, an integrated mocking library, an assertion library, a CLI tool that enables running only certain tests that fit a pattern, and excellent support for various mocking strategies, turn it into a framework rather than merely a library. Jest is used by several large organizations, including Twitter, Instagram, and Pinterest, for React testing.

It is most frequently used for unit testing and is readily expanded to include other integration tests. Among the numerous kinds of automated testing for applications, unit testing is frequently mentioned as being the most crucial. By breaking the application into smaller, completely isolated pieces, unit tests are primarily used to validate the application. Unit tests also guarantee to deliver more output than expected.

It is a special tool for testing and developing a variety of JavaScript library projects, including Angular JS, Node JS, Vue JS, Babel, and Typescript, due to its simplicity-focused design. Jest is incredibly quick and secure, and it can run all tests concurrently to boost performance. It performs previously failed tests first to expedite and simplify the process before rearranging the runs of the next tests, which are based on the large test files.

Jest Features

simple to set up

Setting up Jest is simple because it doesn’t need any configuration or setup. As a result, installing Jest as a prerequisite for a project requires no or very little modification to begin writing tests and delivering them.

Isolated test

When executing tests, isolation is a crucial characteristic. It guarantees that two distinct tests cannot interfere with one another’s operation or affect one another’s test findings. To reduce runtime, Jest tests are executed concurrently within their process. This implies that they are unable to interfere with other tests.

Performance and speed

The jest framework operates quickly. It effectively and promptly executes all of the test cases without any difficulties. The tests can be run in parallel against various setups, and by running those tests first, which takes more time, it can save a lot of time.

Powerful mocking support

Mocking is a method for separating numerous test cases; this separation is accomplished by exchanging the dependencies with objects that can be monitored and controlled. In Jest, mocking often entails changing fake functions for dependencies. All sorts of mocking, including timing mocking, functional mocking, and mocking specific API (Application Programming Interface) calls, are supported by Jest.

Support snapshot testing

Testing of snapshots is possible with Jest.  For front-end testing, snapshots are a crucial feature. Snapshot testing is excellent for comparing the sequencing values of many other frameworks as well as for React Native and React applications. The snapshots enable matching with the saved snapshot and verifying for matching functionality. It requires updating the snapshot file to change the user interface.

In addition to the features already mentioned, Jest also provides some advanced capabilities, such as a CLI tool to control the tests quickly and syntax to test a single test or skip tests with.only and.Skip, and validate almost everything related to JavaScript, especially how online applications are rendered in browsers. JavaScript has excellent documentation with many instances, it has the most active, and helpful community that makes it easier to find solutions quickly when needed.

Jest testing libraries and extensions for Java Developers

As JavaScript continues to grow, developers are working more quickly. A lot of new tools are being developed that could perform better than their predecessors. Because of this, it’s important to always be aware of changes when performing unit tests, integration tests, or end-to-end tests and to pick the framework and toolset that work best for the specific development process. The top 10 Jest libraries and extensions listed below are some of the most widely utilized by Java developers daily.


The most utilized library is Mocha, which is well-liked among JavaScript developers. For asynchronous front-end and back-end testing, test coverage reports, and the usage of any claims library, it is only a test framework that offers browser support for NodeJS applications. Created to operate with Node.js, Mocha is now compatible with a wide variety of frameworks, including front-end frameworks like Jest, React, Vue, and Angular.

For smaller applications without complex assertions or testing logic, Mocha provides a lightweight and easy-to-use solution. Developers may plug in and out most of the supporting libraries and tools in their chain, and it gives them full control over how and with which tools to test the code. Assertions, spies, and mocks are not supported by Mocha, but these features can be added through add-ons or plug-ins.


Chai is a well-known assertion and expectation library for nodes and browsers that support both TDD and BDD (Test-Driven Development). An assertion aids in defining what to anticipate in a test. Any testing framework for JavaScript is compatible with it. It frequently relates to testing with Jest and Enzyme, or with Mocha and Enzyme, respectively. Since Mocha lacks an integrated assertion library, most developers choose Chai with Mocha to test their applications.


Jasmine is yet another top-notch BDD open-source framework and test runner for javascript projects. BDD requires developing tests before writing actual code, in contrast to test-driven development (TDD). Jasmine is not only for writing JavaScript tests—other programming languages like Ruby and Python can also utilize it.

It includes testing the user interface’s response and visibility across a variety of devices with various resolutions. Previously, frameworks like Angular have been utilized via the CLI tool. When testing an application, many developers that utilize the Angular CLI love to use Jasmine. To test the Jest application, developers typically combine it with Babel and Enzyme.

Jasmine is used when a project needs to be integrated with external libraries and is extremely large. Keep in mind that Jasmine requires third-party tools and does not allow snapshot tests, code coverage tools, or parallelization.


Karma is not an assertion library or a testing framework. It is a JavaScript test runner that utilizes Node.js. It also creates an HTML file for the test runner and starts the HTTP server.

Karma enables developers to run JavaScript code on a variety of real browsers.  It was created to make it easier to collect information from tests and write code without making changes to settings. Since Karma is extremely flexible and integrates well-known continuous integration tools like Jenkins and Travis, thus test-driven development becomes quick and simple.


The Jest component can be tested by developers without the need to install anything using an enzyme, which is a testing utility rather than a testing framework. It is one of the most popular frameworks created and maintained by Airbnb. To test the Jest application, it may be integrated simply with other frameworks like Jest, Mocha, etc. React or Chai can be utilized to make its assertions.

The enzyme can access objects, locate elements, interact with elements, simulate events, and render components so that testing its results is simpler. Developers may test Jest components without difficulty using Enzyme’s testing framework because it regularly syncs with Jest’s testing framework. Along with React, Mocha, and Karma or other frameworks, additional Jest testing libraries also use the enzyme.

Other characteristics include good plugin support, usage of shallow rendering, and manipulation of DOM elements, traverse, and even pretending to be a runtime element.


Kent C. Dodds created the React-testing-library, which is supported by an active community of developers. It makes component testing simple and provides user behavior for implementation details in tests.

This package, like enzyme, is a complete collection of React DOM testing tools with a focus on simulating actual user actions and workflows. The React testing library is used by organizations like Graphy, Ze Delivery, Commercetools, and Page Builder. It utilizes test-utils and react-dom as extensions of the former.


Cypress is an extremely quick end-to-end testing framework that makes it possible to write tests without using any other testing frameworks. Without the requirement for driver binaries, it operates flawlessly in Chrome, Firefox, and Edge. Because automated code and application code run on the same platform, full control over the application under test is provided.

When new code is deployed, Cypress’s control panel notifies users of possible distinctions and allows them to monitor the status of the tests. Time travel with snapshots, video and screenshot capture, automatic waiting, built-in parallelization, load balancing for simple debugging, and many more are just a few of the remarkable features offered by Cypress.


The Chrome Development Team created Puppeteer, a headless Chromium Node library. It offers DevTools protocol API for controlling Chrome or Chromium. Developers may launch Chrome, move across pages, get buttons, and click on them using the given API. In addition to this, Puppeteer is capable of generating screenshots and PDF files of web pages as well as automating tasks like form submissions and keyboard inputs. To test an application from beginning to end, it can be integrated with Jest.

Test Renderer

The Test Renderer is a React renderer that offers an easy and simple API used to render React components outside of their native environment, such as on an iOS or Android Smartphone for React Native components. React renderer renders pure JavaScript objects rather than actual components so that tests may be done in Node without being entirely dependent on the DOM or a native mobile environment. It can be used with other testing frameworks, although it is intended to be used with Jest.

Use LambdaTest to execute Jest test scripts.

Each testing framework and library has strengths and weaknesses of its own. The key to getting the greatest result, whether it’s a unit test or an end-to-end test, is selecting and integrating the correct testing framework, like Jest, with the right assertion libraries. While updating, extending, and modifying the code, it aids in the creation of a flexible and adaptable workflow.

It is important to highlight that regardless of the testing framework or library that developers opt for, it is essential to perform Jest tests on a cloud platform like LambdaTest. It offers real devices and browsers to guarantee that all the conditions experienced by real users are taken into consideration during testing.

LambdaTest is an AI-powered test orchestration and test execution platform that enables users to conduct comprehensive testing online using more than 3000 real devices, browsers, and operating systems combinations. For a seamless testing experience, this platform supports all of the major automation testing frameworks and CI-CD tools.

LambdaTest’s ability to track, analyze, and improve Jest app performance simplifies Jest monitoring. Additionally, by leveraging the parallel testing feature of LambdaTest, testers can run numerous tests concurrently.


In conclusion, Jest is a testing framework that is quick, and simple to install and set up. It was created by Facebook and is used by many developers to test all React-based projects and applications. The above-mentioned Jest testing libraries make it simple to quickly test the Jest web application.

Anjali Rishi

Anjali is a dynamic and passionate writer who has found her creative canvas in the world of lifestyle and celebrity entertainment. She is working with bulletinxp.com for about a year now with a fervent love for the written word, she breathes life into her articles, captivating readers with her insightful perspectives and engaging narratives.

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