Frontend Testing

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What is frontend testing?

Frontend in general covers developing the graphical user interface (GUI) of a website, through the use of different technologies (like HTML, CSS, or JavaScript) so that users can view and interact with that website or web app. Essentially, the frontend is the parts of a digital web product that a user can see and interact with.

Frontend testing, therefore, refers to the checks performed to test the usability and functionality of your application’s GUI. Usually, this includes the validation of menus, forms, buttons, and other application elements visible to end users.


Why is frontend testing important?

When you’re developing an application, the most important thing is to ensure the developed application works correctly and is safe for production deployment.

This can be achieved by thinking about the most seamless ways a user can take through your app, optimizing the navigational experience.

While you do of course want to ensure a safe production deployment (i.e. that that app simply works), you also want to make sure that the application stays stable throughout the whole cycle of user interaction. That means that you also need to secure edge cases in vulnerable or critical parts of the application, which can include areas like infinite loading times or error states the user won’t be able to exit from.

The tests you perform to check these things can be either manual or automated, depending on the specific requirements. What you’re essentially doing here is testing the client (browser) part of the application.

Frontend tests provide your app with strong protection against regression. There might be cases where you write code that helps you deploy huge or complex features but might in return crash some other part of the application that you weren’t aware of.

It’s not uncommon for teams or even individual developers to forget some code written a while ago in the process, and then to add new code to the existing one that can cause troubles elsewhere in the frontend.

This will be even more visible in projects with multiple developers. With the increasing complexity of modern applications, it’s rare that you’ll be able to deliver a big project alone. No one can simply know everything about every piece of code written by other programmers. And this is why frontend testing is so important – to double check that code is not inconsistent and the frontend functionality is intact.

You need to build up trust in your code and the final application. Otherwise users may never download your app or delete it after a short time. Whenever a bug appears, found either by your team or users, it should, of course, be fixed – but also covered by an additional test suite so you know it won’t reappear again unexpectedly.

The more you can trust your code, the easier and less stressful deployments will be. Additionally, business leaders will undoubtedly be happier knowing that their application is developing at a stable pace, enabling the company to plan and prepare roadmaps easier.

Another good reason to keep well-maintained tests is that they serve as live documentation. Writing tests requires a proper description of what a specific test (and the component of your application it relates to) does.

What to test in frontend?

Frontend testing is all geared towards performance optimization and enhancing the user experience. Before the advent of Web 2.0 technologies, most web applications were static.

That’s why the majority of processing was done on the server side, meaning performance optimization was achieved through the backend. Now, with applications becoming more dynamic, there is a greater need to optimize the frontend code.

There are several aspects to focus on when testing the frontend of your application. They include:

  • Cross-browser and cross-platform functionality – Checking both the features and responsiveness of your app on different browsers, platforms and devices
  • Accessibility – You need to check that everyone can access your application, including those with visual or auditory impairments
  • End-to-end checks – are required for checking and confirming the end-to-end workflow of the application (backend to frontend) by mimicking the real-world actions users are likely to take
  • Image analysis testing – most websites and apps these days have lots of images on them – from standard display images to logos, infographics and banners. They increase the size of the application significantly, and so you need to run tests to see where you can optimize the images to help the app run faster.
  • Cascading Style Sheets (CSS) testing – CSS is used to help build and style the components of an application. While the user never sees the style sheet code, if it is not written properly, they will definitely see the negative effects of it so you need to run tests to ensure the performance of two main CSS elements: syntax and display. While syntax is rather a domain of developer’s day-to-day work, displayed views need to be tested for regression after changes to specific parts of the app.


Types of frontend tests

Since there are different elements to test for the frontend, there are a few different types of tests you can consider running. Each of these focuses on a different component of your frontend and together will ensure successful frontend testing for your application.

Unit testing

Unit testing is the fundamental building block of frontend testing. It analyzes individual components and functions to ensure they’re working as expected. This is crucial for any frontend application, testing your components and features against how you expect them to behave in production, leading to a stable codebase and a reliable app for your customers. You can also use unit testing for things like edge cases and testing APIs.

Acceptance testing

Acceptance testing is carried out to confirm that user inputs, user flows, and any designated actions on the frontend are coded and functioning properly. Development teams perform them to make sure the final model of the application works as it is expected to by end users.

Visual regression testing

Visual regression testing is a uniquely frontend test. Other types of tests focus on code, and can therefore also be run for backend stacks. In turn, visual regression tests compare the actual/existing interface of your application with the corresponding ‘expected’ version to identify any gaps. This is achieved by comparing screenshots from a headless, server-run browser, and a machine is used to conduct image comparison between them, identifying and highlighting any differences.

Accessibility testing

Accessibility testing checks if an application or website is easily usable by every potential user, including individuals with visual impairments or other additional needs. It is sometimes considered a subcategory of usability testing, and ensures that specific, unchangeable conditions don’t prevent anyone from accessing any of the features or functions of the app, and that they can navigate through the interface as easily as anybody else.

Performance testing

Performance testing analyzes your application’s performance within specific parameters including speed, stability, scalability, interoperability and responsiveness. It is crucial to frontend testing as it helps to ensure that the product sustains its desired quality when the user load is increased, and it is fast and responsive to user requests and actions.

End-to-end (E2E) testing

End-to-end testing is used to check and confirm that the flow of the application works as expected from start to finish. It is mainly done by mimicking the actions of a real user within real-world scenarios to ensure smooth communication between the application’s interface and API is running smoothly. Doing so provides insight into the combined behavior of multiple system elements coupled together.

Integration testing

Most modern applications are built from a multitude of modules. If these modules aren’t properly integrated and working well together, it can ruin the end user experience. You need to run integration tests to ensure everything is working together effectively.

Cross-browser testing

Cross-browser testing is performed to confirm that an application works as expected in different web browsers. This process involves running the same set of test cases on different browsers to check that the application is compatible on each one. Because these tests are the same each time, this process can be automated.


How to create a frontend testing plan?

So you know what to test, why you need to run the tests and know a few different frontend testing tools. But how do you go about putting your frontend testing plan in place? These are the key steps you should follow:

Define your testing budget

Before you purchase tools or hire test engineers, and decide on a timeline, you need to know what your budget is for testing. Usually, this would have been factored into your initial project budget, but it’s good to check expectations against reality when you get to the testing phase.

Choose your tools

Depending on the components and elements contained within your frontend, different tools may do the job for you. Review your requirements against the list of common tools above, or get in touch with a Stutek expert if you’re unsure.

Set a timeline

What is your project deadline? You need to allow enough time for testing and any amendments prior to final release of the application. While deadlines can be strict and give your development team something to work towards, it’s important to be as flexible as possible. After all, you don’t want to release an app that doesn’t work properly, even if it is released on time.

Define the scope of your project

Again, this is likely factored into your initial project plan, but review it again here. In any application development you need to decide on the extent of testing required.

Does the application need to be perfect when you release it, or is it possible to go into production with a working version and see how users respond? Sometimes user feedback can be as useful as the insights you get from automated tests.

Depending on the answer here, you can define the scope of the project so you don’t use more resources than you need to.



As we’ve seen, frontend testing is a crucial activity for a business building a new application or website. It ensures that everything your potential customer sees and interacts with works well, so it can be the difference between a successful product and one that never sells.

It is also quite a complicated process, with lots of tools to choose from, multiple different types and testing and various challenges to overcome. Of course, the scope and budget of your project will impact your frontend testing too, so there’s lots to consider before you get started.

Still unsure? Get in touch with a Stutek expert today to help optimize your frontend performance testing, and empower your development teams to release a successful application to market.

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