What is JavaScript?

  • JavaScript is a programming language which is defined as high level, dynamic and interpreted language used with HTML web applications
  • JavaScript is also used for other than web documents such as PDFs and desktop widgets and became popular for server-side web application
  • JavaScript is object-based script and follows the prototype

JavaScript Unit Testing

JavaScript Unit Testing is a testing method in which JavaScript test code written for a web page or web application module is combined with HTML as an inline event handler and executed in the browser to test if all functionalities work fine. These unit tests are then organized in the test suite.

Each and every suite contains a number of tests designed to be executed for a separate module. Most importantly they don't conflict with any other module and run with fewer dependencies on each other (some critical situations may cause dependencies).

Challenges in JavaScript Unit Testing

There are certain problems one can find while performing JavaScript Unit Testing such as;

  1. Many other languages support unit testing in browsers, in the stable as well as in runtime environment but JavaScript can not
  2. You can understand some system actions with other languages, but this is not the case with JavaScript
  3. Some JavaScript are written for a web application may have multiple dependencies
  4. JavaScript is good to use in combination with HTML and CSS rather than on the web
  5. Difficulties with page rendering and DOM manipulation
  6. Sometimes you find the error message on your screen regarding such as 'Unable to load example.js' or any other JavaScript error regarding version control, these vulnerabilities comes under JavaScript Unit Testing.

To avoid such issues what you can do is;

  1. Do not use global variables
  2. Do not manipulate predefined objects
  3. Design core functionalities based on library
  4. Try to create small pieces of functionalities with lesser dependencies

JavaScript Unit Testing Frameworks

Following is a curated list of popular JavaScript Unit Testing Frameworks and Tools which are widely used :

1. Unit.js: It is known as an open source assertion library running on browser and Node.js. It is extremely compatible with other JavaScript Unit Testing frameworks like Mocha, Karma, Jasmine, QUnit, Protractor, etc. Provides the full documented API of assertion list

2. QUnit: It is used for both client-side as well as server-side JavaScript Unit Testing. This Free framework is used for jQuery projects. It follows Common JS unit testing Specification for unit testing. It supports the Node Long-term Support Schedule.

3. Jasmine: Jasmine is the behavior-driven development framework for JavaScript unit Testing. It is used for testing both synchronous and asynchronous JavaScript Code. It does not require DOM and comes with the easy syntax that can be Written for any test.

4. Karma: Karma is an open source productive testing environment. Easy workflow control Running on the command line. Offers the freedom to write the tests with Jasmine, Mocha, and QUnit. You can run the test on real devices with easy debugging.

5. Mocha: Mocha runs on Node.js and in the browser. Mocha performs asynchronous Testing in a simpler way. Provides accuracy and flexibility in reporting. Provides tremendous support of rich features such as test-specific timeouts, JavaScript APIs etc.

6. Jest: Jest is used by Facebook so far to test all of the JavaScript code. It provides the 'zero-configuration' testing experience. Supports independent and non-interrupting running test without any conflict. Do not require any other setup configuration and libraries.

7. AVA: AVA is simple JavaScript Unit Testing Framework. Tests are being run in parallel and serially. Parallel tests run without interrupting each other. AVA Supports asynchronous testing as well. AVA uses subprocesses to run the test.


  • JavaScript Unit Testing may become tedious and tricky sometimes as it is performed for the front-end basically. One can use the JS libraries to for adding little ease. The challenge might become bigger as JavaScript is getting incorporated with Node.js and TypeScript.
  • You should keep three things in mind while performing the test such as; The feature that needs to be tested, the final output and the expected output. Some tools and framework may help you in performing this task. Above mentioned tool lists is mentioned with most popular and useful frameworks used for JavaScript Unit Testing.
  • More than these with upcoming challenges in performing testing there, some more powerful frameworks and tools may get evolved in future.