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Visual UI or functional testing, which one should I use and when?

I have been confused between visual UI or functional testing, Can antbody please provide me some suggestions regarding whch one shoud use.

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Posted 3 months ago


Being a tester or QA, you might know the importance of testing web applications. It is an essential part of the web application development process on which the stability and success of an app depend. There are many components of a successful web application testing strategy, but two of the most important elements are — Functional testing and visual testing.

As organizations started moving to automation for software testing because it is faster, repeatable, and helps in preventing bugs as well – the test coverage for visual testing is often overlooked with automation because it doesn’t extend checks for visual components of a web app.

It happens with most development teams because they often don’t realize the difference between functional and visual testing. Without proper knowledge of when to use what and why you can miss a lot on your web app testing.

So, here we will talk about functional and visual testing, and why you need both of them when performing web application testing.

Functional Testing

It is a proven fact that without proper functionality a web app will never work as expected. So, functional testing ensures that a web app is working concerning the given requirements. For example, let’s assume that you have an e-commerce web application; it has a menu button on the homepage. Now, if a user clicks the menu button and it displays different options available on your website as expected, then it ensures that your web app is functional; however, if it doesn’t show any other options, then there might be a problem with web app functionality.

Functional testing is performed at every stage of web application testing, i.e., from unit tests to end-to-end test cases. It is essential to make sure that user flows are working as intended and consistent with the development team’s vision. So, apart from the menu page, you may also need to check that clicking any option from the drop-down menu will redirect you to the correct page.

You can continue performing functional tests with adding items to the cart and then checking out to make sure each of the functions is working properly one after another and allow users to purchase without any interruptions. And this process is not only applicable to one OS or browser, but you also need to perform these functional tests across a combination of OS, browsers, and devices as a user can access your web app from any source. It can be easily achieved with automated cross-browser testing.

The main goal of functional testing is to measure all the workflows of a web app by analyzing its graphical user interface. Here are functions that need to be defined with functional tests:

  • Navigation
  • Links on a page
  • Pop-up or confirmation message
  • Create, edit, update and delete tasks
  • JavaScript is working properly in all browsers
  • Search and display the desired results If you’re working as a tester, QA, or developer for a long time, then these points are not new to you, but, differentiating between visual and functional testing, and understanding when to use them will help you create a better testing strategy.

Visual Testing

Reading the above points, you might have understood the importance of functional testing for your web app. But, many development teams still make the mistake of performing bulk tests for web app functionality without considering visual tests.

Visual testing is the process of checking how your web app looks in addition to how it works. It often happens with testers when the UI of web apps pass a functional test without observing the defective design elements.

When users scroll through your website, they not only look at the workflow but also check the responsiveness of a web app. And if a web app is not built to be responsive, then the design elements may differ on different devices or browsers that compromise the user experience.

Every user expects a consistent flow when they visit a website, but visual bugs are annoying and unpleasant, which makes users abandon your site immediately. If a user is about to complete a purchase on your e-commerce store, visual inconsistencies can stop them from completing their action even if your app has proficient functionality.

The main goal of visual testing is to track and eliminate visual defects in the UI of a web app. Performing visual tests ensure that the user interface is perfect from a user’s perspective because there is no other way to know that a recently updated visual component has broken due to an automated functional test. Here is a list of things that needs to be checked while performing visual tests.

  • Check if any component is hidden or overlap with any other UI element
  • Make sure each UI element appears in the right color, size, shape, and position
  • There are no broken images on any web page
  • Changes made on one screen doesn’t affect the layout on another screen size
  • The app appears the same on every browser, OS, or device

Most of these things can be checked and verified if you perform automated cross-browser testing with LambdaTest, but, it’s necessary to perform both functional and visual test on a web app, here why!

Why Do You need to Perform Both Functional and Visual Testing?

As mentioned above, development teams have started adopting automated functional UI testing over manual testing techniques. If you're one of them, then let me ask you one thing – how often do you change or modify the CSS for your web app?

As we all know that a lot of things have been changing with the evolution of technology. Now, the web and mobile applications are designed with the advanced user interface, AJAX, responsive layouts, and JavaScript. Therefore, if any changes are made to a website, it is crucial to perform both functional and visual testing to ensure that it works properly with different screen resolutions, browsers, and responsive designs. Here are some points that show when and why you should perform both these tests.

  • Browsers Update – These days vendors are updating their browsers more often and automatically. So, most users don’t even get an idea when their browser has been updated. To keep up with every browser and user expectation, it is necessary to perform both the testing.

  • Screen Resolution – Users can access your website on any device – it can be a mobile, desktop, or laptop. So, it is necessary to make sure your web app is compatible with every screen size.

  • Responsive Designs – Responsiveness of your web app makes a huge impact on user experience, and it can only be ensured with functional and visual testing.

Functional changes can be detected easily, but finding visual mistakes is not that simple, especially with automated functional UI testing. Therefore, it is crucial to perform both of these testing processes separately.


Software testing is a critical step in the development process as it requires proper attention and every test needs to be executed carefully, but, most development teams often ignore the importance of visual testing over functional testing. This blog highlights why and when you need to perform both these tests on your web app.

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Posted 3 months ago