The Utility of JavaScript Unit Testing Frameworks

Explore various ways to use JavaScript frameworks for frontend and backend capabilities. Know how some of the best JavaScript unit testing tools are used in the industry!

In its simplest form, JavaScript or JS is an interpreted, multi-paradigm, event-driven, functional, and high-level programming language with imperative style (object-oriented and prototype-based) that essentially confirms to ECMAScript specification. Having curly syntax, dynamic typing, first-class functions, and prototype-based object-orientation. JavaScript has gradually become the language of the web with both client-side as well as server-side scripting. It is an open-source library, which runs on browser and Node.js.

Conjugated with the web development scenario, programmers have added upon their traditional knowledge and strategies of Java, .Net and PHP along with prevalent JavaScript Frameworks owing to ease of use in frontend as well as backend and rapid prototyping capabilities.

Understanding why frameworks should be used?

A software framework is derived after abstraction of a programming language which incorporates generic functionality that can be selectively changed by writing additional user-written code. JavaScript framework is such an application framework written in JavaScript where the programmers can manipulate the functions and use it according to their convenience.

Frameworks, in general, make it easy for the programmers to make use of a particular programming language, making the application more responsive. Popular JS Frameworks in 2019 are:

  • Angular
  • React
  • Vue.JS
  • Ember.JS
  • Meteor
  • Mithril
  • Node.js
  • Polymer
  • Aurelia
  • Backbone.js

Introduction to JavaScript Testing

This also calls for the need to have tools that support both front end as well as backend, with low overhead and zero external dependencies, leverage asynchronous nature of javascript, runs concurrently, Single framework fit for NodeJS, VueJS, React, Angular etc, Allows to run tests remotely onto other devices, Can be used to run tests on browsers, headless environments like PhantomJS as well as on devices, Supports test case debugging using Chrome as well as Webstorm, Supports ES6, Typescript and coffee script standards, provides automation support for form submission, UI testing, and keyboard inputs and many more features. QUnit is one such JavaScript Unit Testing tool that can be used on both client-side and server-side. Prompts like “Unable to load example.js” or any other JavaScript error regarding version control comes under JavaScript testing.

A JavaScript application can be tested in three different ways:

  • By testing individual functions where inputs are provided to determine a predefined output. (Blackbox testing method). This is known as Unit Testing.
  • In a second way, the application as a whole component is tested to see if expected results appear. This type is called as Integration Testing.
  • In a third way, the browser is controlled without checking how the application is going to perform. This type is known as User Interface Testing which involves checking the screens with the controls like menus, buttons, icons, and all types of bars – toolbar, menu bar, dialog boxes, and windows, etc. and meets all specifications.

In-Depth: JavaScript Unit Testing

JavaScript unit tests are usually arranged in a suite, run in browser or frontend. These can even be written for testing a webpage or a single module of the application. This code can be combined with HTML to work as an inline Event Handler. If a test is created for testing an individual module, it will run independently without interfering with other modules and runs fewer dependencies on each other.

Exceptions with JavaScript Unit Testing

JavaScript testing isn’t without exceptions. Problems one can find while performing JavaScript unit testing can be:

  • JavaScript cannot be used for cross-browser unit testing in stable or runtime environment.
  • DOM manipulation and page rendering are not easy with JavaScript.
  • JavaScript written for web applications can have multiple dependencies.
  • JavaScript performs well along with HTML and CSS instead of on the web.
  • It is not easy to understand system actions with JavaScript, therefore other programming languages have to be used.

What Should Be Done To Avoid Above Exceptions with JavaScript Testing Frameworks

  • Global variables must not be used.
  • Predefined objects must be kept as such and must not be manipulated.
  • Core functionalities must be designed based on the library.
  • Functionalities must be created according to modules with lesser dependencies.

Best JavaScript Unit Testing Framework and Tools

Examples of some prominent JS testing frameworks that help in JavaScript Unit Testing:

  • JSUnit
  • Unit.js
  • QUnit
  • Jasmine
  • Karma
  • Mocha
  • Jest
  • AVA
  • Sinon
  • ChaiJS
  • Puppeteer
  • Cypress.io
  • Tape

Succinct

Although JS libraries can often be added for convenience, still JavaScript Unit testing might often become cumbersome and complicated sometimes in case only front-end is considered. The problem might enlarge when JS is combined with Node.JS or TypeScript. Top web development companies must consider following three points while starting with JS Unit Testing: (1) what features are to be tested, (2) what will be the final output of testing the application (actual vs. expected results), (3) what tools and frameworks should be used in performing this task. The tools mentioned above (updated till July 2019) are the most useful ones for JS unit testing.