An Introduction to Frontend Unit Testing


If you are a web developer (or enthusiast), you have probably heard of the term "unit testing" being used quite frequently. And you may have wondered why we need to perform such "tests" on our applications. Well, worry no more, because, in this blog, we're going to explore exactly what unit testing is, why we need it, and how we can implement it!

What is unit testing all about?

Unit testing isn't a concept limited to just web development. It is merely a technique (or method) in which we select individual modules, that is, smaller chunks or blocks of code, and test it against various conditions and operations, and check whether the application performs as it is supposed to.

Unit testing doesn't just check what the application is doing, it also provides insights into how efficiently it is doing the task assigned. This can help developers write cleaner and more efficient code, with less effort and in less time. Oh, and did I forget to mention the most obvious use of testing? For resolving bugs! Some bugs can be notoriously difficult to find without testing your application, and also very hard to debug. However, unit testing simplifies this task to a great extent. Furthermore, cleaner code could significantly improve performance - which could reduce memory usage and other resources!

Frontend Unit Testing

The frontend part of a web application, the part that is actually visible to the client-side, typically consists of plenty of pages, each with its own functionalities. Usually, multiple frameworks and libraries are used for building the frontend, such as React.js, Angular.js, Bootstrap, GSAP, and many more. Some focus on design and the overall look of the website, while others are more logic-oriented and for performing specific functions.

Perhaps the most essential and basic kind of test a web developer must perform is a cross-browser compatibility test. The name itself is self-explanatory - we test our application on different browsers and check to see if everything is fine. Usually, some browsers may not support a particular CSS property, or JavaScript function, and you may need to provide additional lines of code to make the app cross-browser compatible.

So how is testing actually performed?

There are a handful of easy-to-use and flexible frontend testing tools available that you can use to effectively test your web apps. For the browser-compatibility test mentioned above, you can use LambdaTest, which is a quick and easy platform where you can perform automated web testing using its scalable, secure, and reliable cloud-based Selenium grid on a combination of 2000+ real browsers and browser versions to maximize your test coverage. Do try it out!

Next, take a look at Jasmine, which is a development framework for effectively testing JavaScript Code. You'll probably be using JS a lot in your websites and web apps, so do take a good look at this framework!

No website or web app is complete without its CSS, and its testing is equally important to perform. Needle is another such testing framework that provides tools to ensure proper alignment, positioning. It takes screenshots of the rendered DOM and compares them with the ideal, known screenshots in order to check if the visuals render correctly.

Lastly, but certainly not the least, check out Selenium, which is actually a browser-automation tool, but can also be used for testing purposes. It performs end-to-end testing across various browsers and platforms like Windows, Mac, and Linux. It allows you to write tests in different programming languages like Java, PHP, C#, etc. The tool offers records and playback features to write tests without a need to learn Selenium IDE.

So what's next?

With practice, comes perfection! It may seem overwhelming to hear so many new names in one go, but once you start using these tools, they'll become a part of your everyday routine. But unit testing, as mentioned in the introduction, isn't just limited to the frontend - in fact, testing the backend is equally or even more important. Important databases, credentials, and other sensitive information all lie beyond the depths of the client-side. And a single vulnerability is all an attacker needs to devour an application.

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