Understanding Unit Tests in Javascript: 5 Frameworks

When it comes to testing, checking a single function is different from testing a complete application at once. It helps to understand the flaws in any units of the application and allows the developers to take appropriate steps. 

How unit tests beneficial to you?

Testing a single functionality is often referred to as unit testing. It is done to ensure that every individual function performs as expected. A unit test verifies and substantiates the behavior of a particular unit of the application. Simply put, the unit test verifies if the isolated part of the software in the codebase behaves as interpreted and expected by the developer. 

Unit testing helps developers compare the actual behavior of the software unit in complete isolation with the expected behavior. The term complete isolation here denotes that the developers do not connect the software unit under test with the external dependencies. For example, devs do not connect MySQL database with PHP, a filesystem, or any HTTP services. 

Unit testing makes the coding and development process more agile. On Adding more features to the application, developers sometimes need to change its previous specification, which affects the overall functioning of the software. To detect this during development time, developers perform unit testing on each event of addition or deletion of features. 

Web developers also focus on unit testing to improve the quality of code by identifying defects and errors before sending the application for integration testing. The overall process helps facilitate modifications and simplifies integration. The accuracy of each unit is tested to ensure no discrepancies remain in the code and everything is up-to-the-mark. 

Usually, code tests are written prior to even the software code, and this strategy is referred to as test-driven development (TDD). When testing codes in Javascript, developers can try various frameworks.

JavaScript testing frameworks

Frameworks for unit tests in JavaScript
Frameworks for unit tests in JavaScript


An assertion library that runs on web browsers and Node.js. This framework supports an array of unit test running platforms used for e2e and ui-tests. 

Unit.js is open source and can be used for business as well as personal projects. Developers can generate and download API spec documentation from the unit tests into HTML, JSON, and Markdown for easy understanding and processing. 


Jasmine is among the most popular Javascript libraries known to be behavior-driven development frameworks for Javascript unit testing. Automated test utilities help verify bugs in the synchronous as well as asynchronous code alike.

The availability of CLI (Command Line Interface) allows developers to run tests and check output in the terminal. Using Jasmine, the devs can organize the set of tests by nesting suites into the top-level suites. Jasmine is designed to run over any Javascript-enabled platform (see example here). 


Another significant unit testing framework for Javascript, Jest, is open source. When you need to perform tests on front-end platforms with time-consuming and resource-intensive configurations, Jest can be an ideal option as it reduces the complexity greatly. 

Jest supports unit testing for Javascript frameworks and libraries. Not only is it easy to set up but speedy too as they run tests in parallel. On installing Jest, you will get access to a huge mocking library, spies, and a built-in matcher.

You can see an example usage of Jest here.


End-to-end, Javascript-based testing framework developed on Mocha framework. Unit testing in Cypress can be executed without running a web server, and this feature makes it an amazing tool for testing a Javascript library. 

Cypress is popular mainly because it doesn’t demand a setup. With an interactive interface, the framework runs on browsers and is highly supportive of Windows, Mac, and Linux operating systems. The test runner automates video capturing and screenshots. 


Once, Mocha was considered to be the best testing framework for unit testing, but the demand records declined with the introduction of other advanced and high-end testing platforms. 

Developers can use Mocha for testing front-end as well as back-end platforms. It provides a clean base for writing codes and can mock objects for performing flexible tests. Mocha is also considered an ideal testing platform for large projects.


Javascript is highly used in the development domain, particularly for developing web pages. The language empowers developers to add dynamic features and functionality to the webpage. Special effects make the end product more intuitive and interactive. 

Learning the unit testing frameworks and platforms for Javascript-based applications can be a great idea to be able to pick the best testing option for your product.

Featured Image by Ferenc Almasi on Unsplash

Sign up to my newsletter to enjoy more content:

5 1 vote
Article Rating
Notify of

Inline Feedbacks
View all comments