Quality Engineering
min read
June 28, 2022
November 9, 2021

Everything you need to know about automated visual regression testing

Everything you need to know about automated visual regression testing
Table of contents

Regression testing is a form of software testing that involves executing functional and non-functional tests again and again. These tests are carried out to guarantee that previously designed, and tested software continues to function properly even after a modification has been made. It primarily examines if an application's UI is still looking good once a new feature has been implemented. In addition, it is a verification procedure that looks for any new flaw or fault in the current software. 

Impact of visual errors on the user experience

When we talk about visual mistakes, we're not talking about logical problems in the system; we're talking about aesthetic flaws that cause interfaces to appear improperly, degrading the user experience. 

Some of the common UI defects are as follows:

  1. Issues with the font (instead of text, there are unknown markings) 
  2. Issues with alignment 
  3. Issues with layout 
  4. Issues with rendering 
  5. Elements that overlap 
  6. Issues with responsive layout 


Most consumers will not return to your website or app if they have a poor experience visiting it. In addition, users don't like to visit websites with fundamental issues. Therefore, the content of the website should be clear, concise, and crisp.

Visual errors are issues with the design or layout of an online or mobile application's interface. As a result, users may experience application problems when they visit your app or website. In addition, these visual flaws wreak havoc on an app's user experience. 

What exactly is automated visual regression testing, and why should you care? 

Visual regression testing is done to conduct UI or front-end regression testing by gathering screenshots of the UI and comparing them to the original or baseline pictures. If there is a slight variation from the baseline image utilizing the captured mobile UI, the visual regression mechanism will alert you and highlight the pixel-by-pixel problem. 

Visual testing examines an application's visual output and compares it to the results predicted by the designer. Visual tests may be conducted at any moment on any application with a graphical user interface. Most developers conduct visual tests on individual components during development, and during end-to-end testing, they run visual tests on a fully functional program. Thus, a regression test functions similarly to a verification technique. However, test cases are often automated as they must be executed repeatedly, and it can be tiresome to execute the same test cases manually. 

Programming languages, such as Java, C++, C#, and others, are not required for regression testing. Instead, it’s a type of testing utilized to see whether the product has been modified or if any updates have been made. It ensures that any changes to a product do not disrupt the product's current modules. 

Case scenario for visual bugs 

automated visual regression testing

Here's an example of a visual flaw in Amazon's mobile experience: the filter bar covers the product description, which is inconvenient for shoppers who want to read it quickly. Of course, the issue is inconvenient in this situation, but there are other times when a visual fault renders a program useless. For instance, when a visible component shifts or vanishes entirely. 

Once the developer has fixed the problem, it must be re-tested. Regression testing is also required because while the price on the reported page may have been corrected, it may still show an incorrect price on the summary page. The total is displayed alongside other charges or in the email sent to the customer. Unfortunately, automated UI tests aren't designed to check for visual errors. Thus they'd miss this one. Even tech titans, as seen in the Amazon example, are not resistant to these flaws. Visual mistakes in an application are conceivable as automated UI testing does not discover them. It's critical to find these issues since they may significantly influence an app's usability and accessibility and the user experience. 

If a visual problem prevents a user from accessing an application's core functions, it should be reported as a functional bug. 

Function vs. design             

While it is self-evident that you must examine your website for regression, many individuals mistakenly believe this includes the aesthetic element. On the contrary, visual regression testing is unique from functional regression testing. It examines whether any new code has hampered the functionality of a page. In contrast, functional regression testing examines whether the latest code has impeded the usability of a page. 

There are several browsers, mobile devices, and screen sizes to consider for web development. For example, a single page in the system may be displayed by Chrome or Firefox, viewed by small, medium, or large desktop displays, and browsed by various operating systems on mobile devices with various screen sizes. 

Understanding the difference is critical since a visually "altered" page may work perfectly and pass all functionality tests. When we consider browser rendering and responsive design, where the web pages are autonomously scaled, and some components are concealed, reduced, or extended to look good across all screen sizes, the difference becomes even more apparent. 

Unfortunately, functional testing doesn't pick up these more subtle design changes regarding user involvement, which can vary from moderately uncomfortable to outright unpleasant and disruptive. 

Visual compatibility 

Visual regression testing becomes even more necessary when dealing with responsive systems to discover compatibility issues while rendering websites. Furthermore, those tests may detect some of the cross-platform issues that are more difficult to detect. Websites or web pages must be visually perfect in all screen sizes and all operating systems. It must be compatible with all screen sizes and should be responsive.

Opera or Chrome might display a single page in the system, viewed on small (under 6-7 inches), medium (10-12 inches), or large (desktop) displays, and browsed by several operating systems on mobile devices with a wide range of screen sizes.

How does automated visual regression testing work?

Automated visual testing is a method of determining if a user interface appears visually as intended. If you need regression visual testing to deal with frequent changes to a stable UI, automation is a smart option. Automated testing also aids in a great visual comparison of screenshots. 

The advantages of automating visual tests are that they save money in the long run. In addition, they are faster and accurate than manual tests because they can eliminate human errors and deliver pixel-perfect visual tests, are reusable, and are transparent because they provide automatic reports that are easily accessible by anyone on the team. 

Automated snapshot comparison improves the precision of visual inspection while also increasing the return on investment. Bugs that are hard to identify with human eyes and manual comparison can be captured with automatic snapshot comparison. It's also beneficial for complicated user story end-to-end testing. 

  1. Drive the program and test it, as well as take screenshots at this stage. 
  2. The automation engine compares these screenshots to the baseline screenshots in this phase. The baseline screenshots are often photos captured during prior test runs and verified by a tester. 
  3. When the program receives the results of the picture comparisons, it creates a report with all of the discrepancies highlighted. 
  4. When the tool receives the results of the picture comparisons, it creates a report that summarizes all of the differences discovered. 

Manual regression testing vs. automated

When manual regression testers do regression testing, test cases are first written and then executed. These tests assist in determining if a test is a pass or a fail based on the expected results specified in the test cases. Automated regression testing entails many stages. The generation of effective test data and the development of quality test cases are critical for test computerization. There are various automated regression testing solutions available, and organizations should choose one based on the application being tested. 

How to implement automated visual regression testing?

Testing is just repeating a process in a given circumstance for a specific reason. As a result, we can confidently deduce that the same approach used for testing in the first place may also be used for this. As a result, if manual testing is possible, so is regression testing. It is not required to utilize a tool. However, as time passes, programs get increasingly bloated with features, growing the danger of regression. Therefore, this testing is frequently automated to make the most of the time. 

Visual regression testing should be automated and integrated into the CI/CD workflow. This saves time, minimizes the risk of human mistakes, and guarantees that the software's aesthetic attractiveness is maintained. 

  • Create scenarios for testing. Define what should be recorded in screenshots and when they should be taken during the test. Be careful to incorporate a range of user interactions in these situations, as the software will have to deal with them in the real world. 
  • The program that compares new screenshots with older screenshots using an automated visual testing method will provide a report that lists all of the changes found. 
  • Critics examine whether the modifications made resulted in the intended outcomes or whether there were any interruptions. 
  • If any bugs are discovered, they must be repaired. Update the updated screenshot as a reference point for upcoming visual regression testing once that's done. 

Benefits of automated visual regression testing

Automated visual regression testing tools analyze pictures "pixel by pixel" to check for changes caused by faults or bad practices. It allows businesses to guarantee that these changes do not negatively impact the final product experience.

  1. Hundreds of claims can be replaced with a single visual picture. 
  2. Automated visual testing examines the user interface in a variety of browsers, displays, and devices. 
  3. We can highlight significant differences in material and small-scale UI.
  4. It helps to improve the product quality and user experience.
  5. It helps to improve the ability to make functioning automated checks.
  6. The process of checking accuracy has improved.
  7. This frees up time for test analysts to focus on interpretation and more difficult challenges.
  8. Great visual design contributes to the development of trust and credibility.

Where and when not to use visual regression testing?

Automated visual testing analyzes the graphic look of a test application and compares the results to known excellent screenshots to see whether they match. In addition, this method evaluates graphic value criteria such as paint consistency, alignment, size, etc. 

If you are short of time, you should avoid using this method. Visual regression testing is time-consuming and should not be utilized unless you have a strict deadline. Neither automatic nor entirely manual visual regression testing is possible. It is preferable to use a combination of automated and manual visual regression. When comparing pictures, don't rely on tool error configuration ratios. 

Visual regression testing is one of the most reliable ways to reach the desired output. The essential factor is whether the human eye can detect the change is put into the system of this testing method.

Visual testing is used in conjunction with functional testing to analyze the visual quality while testing an application. This is challenging for functional automation frameworks to capture because they are designed and implemented to focus solely on functional elements. 

Tools for visual regression testing

Let's have a look at a few tools for visual regression testing: 


The complete visual UX testing solution and visual validation is Kobiton's scriptless automated visual testing solution. In addition, Kobiton is a mobile testing tool that offers complete visual validation and visual user experience testing for mobile devices. 


BrowserStack's Percy is an automated visual testing platform designed for task forces to conduct automated visual validation tests. It enables you to create, develop, and distribute software. Smart visual regression testing, responsive visual testing, and cross-browser testing are all supported. 


Applitools Eyes is a cloud-based facility for automatic visual UI testing of mobile, web, and desktop applications from Applitools. It verifies the visual output of your UI across a variety of browsers, operating systems, devices, and screen sizes.


BackstopJS is a JavaScript-based framework for visual regression testing. BackstopJS sees your website just as a black box, so you don't need to write your website in JavaScript to use it. One of its features is very detailed and helpful as it points out the differences among your pictures, which is included in the report it creates.


Chromatic aids in the consistency of UI elements. It captures pixel-perfect images of rendered code, style, and assets in real-time. In addition, every commit to the repository is automatically checked in the cloud for visible changes.


Teams may use Screener to examine their UI across various operating systems, browsers, and other electronic devices. It detects visual regressions and inconsistencies in the UI automatically. It shows changes by comparing screenshots and DOM snapshots. 


Regression testing is a proven method of ensuring that an application stays defect-free even after several modifications. It also guarantees that no current functionality has been harmed as a result of the recent changes. Regression testing should be used to discover issues in a new software release while also ensuring that prior defects have been addressed. Any new feature should be subjected to regression testing, validated using an efficient regression test automation approach, and maybe checked manually or using an automated regression testing framework and tools.

There are a variety of automated visual regression testing solutions. Choosing one may be influenced by your demands and budget, as well as the goals you wish to achieve. QED42 is a full-service solution provider that uses design and technology to create ambitious digital experiences for consumers worldwide. 

It helps companies reinvent themselves to provide superior data-driven online, mobile, and social experiences. Our intelligently crafted online and mobile experiences have earned us the confidence of over 200 worldwide customers. Sony, Intel, and others are among our notable clients. In addition, our extensive knowledge in Drupal, JavaScript frameworks, and design thinking can convert organizations into intelligent enterprises.

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