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Visual Regression Testing: Everything You Need to Know

April 18, 2024Veselin Mladenov
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Visual Regression Testing: Everything You Need to Know in 2023
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Regression testing ensures changes to the source code do not cause issues to the existing system. Or it also sees if software functionality has regressed. Visual regression tests focus on how the user will receive the final interface of the product. How the user interacts with the application is essential and paramount to the visual aspects of the web pages.

What is Visual Regression Testing?

Visual Regression testing is checking the UI accuracy of an application, website, or software after any code changes.

Visual bugs are giant bugs that affect the user experience of using a website, app, or software. They’re the most apparent to users because they will be part of the first impressions a user gets.

It is also useful for apps for similar reasons. Ensuring that buttons work, the text is visible and readable, and ads do not cover any visual element.

It generates, analyzes, and compares browser screenshots. The goal is to detect if any pixels have changed. The differences are called one of the following names: visual diffs, perceptual diffs, CSS diffs, or UI diffs.

Why Visual Regression Testing?

Ensures costly visual glitches do not slip through to the production stage. Neglecting visual validation can significantly undermine the user experience and, in many cases, lead to a loss in revenue.

How Visual Regression Testing Works?

To do visual testing, one must have a test runner to write and run the tests and a browser automation framework that can replicate the actions of users. There are plenty of programs that can replicate user functions. Then the visual testing program will capture screenshots throughout the process. These are all compared to the initial screenshots taken as a baseline before testing began.

Any time a change is noticed, a screenshot is captured. Some testing tools even go so far as to highlight the differences that were noticed from the baseline. Then, reviewers determine if the issues are because of the bugs in the code that developers need to fix. It can also be because of something with ad integration that must be addressed.

How do Visual Regression Tests Determine the Issue?

Visual regression tests use screenshots to determine where issues may arise or have already arisen because something has regressed. It is useful in finding where a visual bug might have been introduced into the system.

For example, this could be due to overlapping text making part of the page unreadable or text crowding a button out of functionality. It also checks for ads covering the page, causing text to be unreadable or buttons and links inaccessible. This can also happen due to compatibility issues between browsers, screen sizes, and operating systems. Thousands or millions of device-screen size-resolution-operating system-browser combinations and configurations can change how to code and display pixels.

How to Implement Visual Regression Testing?

There are different ways to implement Visual Regression testing as per your need. But one of the most common techniques to validate the UI accuracy of your application for end-users is by comparing the before-after screenshots.

  • Generate the test scenarios and define what to capture and when to capture the screenshots.
  • Use an automated visual testing tool to compare the newly taken screenshots (after changes in the code) with the already existing images of the application. Testsigma supports such implementation to run your visual tests.
  • Check for UI discrepancies or issues to report these changes in the latest product design.
  • If you come across any visual bugs, fix them and update the screenshot as the baseline image with the new picture to use for future Visual Regression tests.

Importance of Visual Validation Testing

Visual regression testing is crucial because if a site is unreadable or an app is not functional due to a mistake in the visual interface, people will click away from the site or delete the app. After all, they are not benefitting from it. This hurts revenue.

The user experience is essential for getting maximum revenue. The user interface must not only be functional, but it must also provide the user with the best experience possible to keep engagement up. One way to ensure a visually appealing interface is by incorporating a well-designed logo that reflects your brand identity. Engagement is the key to ad revenue, SEO, and many other aspects of running a website.

Additionally, having an exemplary user interface and experience will ensure a site builds trust and credibility with its user base. It also reinforces brand image, guides users towards desired actions, and persuades the eye to pay attention to key page elements. Not to mention this is where overall legibility and functionality come into play. A clean, visually balanced website is crucial for all of this.

Even the smallest distortion in the user interface can be inconvenient at best and detrimental to business at worst.

This is also why testing for multiple devices, browsers, operating systems, and everything else is important. While developers cannot necessarily account for every screen size and resolution the end user might be using, they need to do the legwork to ensure that Apple, Android, Windows, and other operating systems are getting the same experience. The same goes for the difference between mobile and desktop.

Different Methods of Visual Regression Testing

Several methods are available for visual regression testing, each with advantages and limitations. Let’s explore some of these methods:

Here is a brief explanation of each of the different methods of visual regression testing:

  • Manual visual testing: This is the simplest method of visual regression testing. A tester manually compares UI screenshots before and after changes. This method is time-consuming and error-prone but can be effective for small projects or testing specific UI elements.
  • Layout comparison: This method compares the UI layout before and after changes. This method is more efficient than manual visual testing but can be less accurate, as it needs to account for changes in the UI’s color, font, or other visual elements.
  • Pixel-by-pixel comparison: This method compares the pixels of the UI before and after changes are made. This method is the most accurate, time-consuming, and computationally expensive. This method is best used for small, complex UI elements or testing UI elements critical to the user experience.
  • Structural comparison: This method compares the UI’s DOM (Document Object Model) before and after changes are made. The DOM is a tree-like structure that represents the HTML of the UI. This method is more efficient than pixel-by-pixel comparison, but it can be less accurate, as it needs to account for changes in the UI’s CSS (Cascading Style Sheets).
  • Visual AI comparison: This method uses artificial intelligence (AI) to compare the UI before and after changes. AI-based methods are becoming increasingly popular, as they can be more accurate and efficient than traditional methods of visual regression testing.
  • DOM-based comparison: This method compares the DOM of the UI before and after changes are made. This method is more efficient than pixel-by-pixel comparison, but it can be less accurate, as it needs to account for changes in the CSS of the UI.
  • Creating dedicated visual regression tests: This method involves creating custom tests that specifically target the UI elements that need to be tested. This method is more efficient than using a general-purpose visual regression testing tool, but it can be more time-consuming to set up.
  • Inserting visual checkpoints: This method involves inserting checkpoints into the UI that can be used to check the visual state of the UI at specific points in time. This method is more efficient than creating dedicated visual regression tests, but it needs to be more accurate, as it only accounts for some possible changes to the UI.
  • Inserting implicit visual validation: This method involves using implicit visual validation to check the visual state of the UI. Implicit visual validation is a technique that uses the browser’s built-in validation capabilities to check the visual state of the UI. This method is the most efficient but needs to be more accurate, as it only accounts for some possible changes to the UI.

The best method of visual regression testing for a particular project will depend on the size and complexity of the project, the budget, and the desired level of accuracy.

Benefits of Visual Regression Testing

Here are some of the benefits of running visual regression tests:

Improved user experience: Visual regression testing can help ensure the UI is always consistent and visually appealing, leading to a better user experience.

Reduced costs: Visual regression testing can help reduce costs by catching bugs early in development. This can prevent costly rework and customer support issues.

High product quality: Visual regression testing can help ensure the product meets its quality standards. This can lead to increased customer satisfaction and repeat business.

Here are some additional benefits of visual regression testing:

Allows test analysts to devote more time to interpretation and real-world problems: Visual regression testing can automate many repetitive tasks involved in UI testing, freeing test analysts to focus on more complex tasks.

  • Displays material and small-scale UI variations: Visual regression testing can detect even subtle UI changes, which can be essential for ensuring a consistent user experience.
  • Visual element comparison across several browsers: Visual regression testing can compare the UI across different browsers, ensuring the UI looks the same on all platforms.
  • It entices the user to pay attention to specific page elements: Visual regression testing can highlight essential page elements, which can help improve the user experience.
  • Ability to increase the value of functional automated checks: Visual regression testing can complement functional automated checks, providing an additional layer of assurance that the UI is working as expected.

Overall, visual regression testing is a valuable tool that can help improve software product quality. If you still need to start using visual regression testing, consider it.

Manual Visual Regression Testing vs Automated Visual Regression Testing

As stated previously, manual visual regression testing can be good towards the beginning of development. Still, ultimately, it will take up precious time and resources because it is such a repetitive task. Automated visual regression testing frees up the developers and engineers to resolve bugs or create new features.

Manual Visual Regression Testing:

  • It tends to grow larger with every new feature and functionality added to the software, which increases the amount of time a human person must spend pouring over screenshots to determine bugs.
  • This becomes a more significant issue when there are tight deadlines to contend with.

Automated Visual Regression Testing:

  • Automating the repetitive need to check the page after every code change is useful.
  • However, with some of the issues mentioned above in the different types of visual regression testing, which is the best option? Manually, falsely identifying or missing issues is possible, which still ties up developer and quality assurance hours.
  • Utilizing a trainable AI is certainly an intelligent option, though it has costs. However, with the appropriate amount of time and money spent upfront, automated visual regression testing will save you time and money in the long run.

Automated Visual Regression Testing Use Cases

A use case of Visual testing is going through a webpage and discovering UI issues that make browsing an unpleasant experience. For instance, overlapping texts/images, hidden/unclickable buttons, broken images, or alignment issues are usual visual bugs you can find online. All of these errors influence user experience negatively and impact business performance.

Visual Regression Testing Example

Let’s consider a few examples of Visual Regression testing for your better understanding:

  • A submit button on the sign-up page is broken after reworking the complete layout of the page
  • A drop-down menu does not slide down after clicking on it after adding more options to it and increasing the pixels of the options
  • A slideshow of images on the homepage has some broken/missing pictures after updating it in the backend

All of these UI errors need attention as new changes to these elements resulted in breaking the visual aesthetics of the page.

Limitations of Traditional Visual Regression Testing Approaches:

Here are some of the limitations of traditional visual regression testing approaches:

  • They can be time-consuming and expensive to set up and maintain.
  • They can be brittle and sensitive to changes in the rendering engine or the display device.
  • They can be less effective at detecting subtle changes to the UI.
  • They need to be more accurate at detecting changes to dynamic content.
  • They can be challenging to scale to large and complex UIs.

Despite these limitations, traditional visual regression testing approaches can be valuable for ensuring UI quality. However, choosing the right approach for the project’s specific needs is essential.

Best Practices for Automated Visual Regression Testing

Here are some best practices for running automated visual regression testing or automating regression testing in general.

1. Modifications need to be easy. The AI should suggest relevant bugs and visual differences and give workarounds for fixing them. Then developers can make the edits without too much hassle.

2. The AI program should utilize reusable test steps. The features need to be recorded so they can be readily available for the test team to use and reuse – preferably with only the smallest bits of edits required in between test runs.

3. The test automation should be scriptless and provide automated test cases ready to use with reusable code objects. This also solves coding issues because the automation tool handles the process and makes testing faster.

4. The automated regression testing tool should be integrated with any continuous integration tools already in place to verify the website or application when the cycles are run.

5. Testers reuse methodologies for all similar cases and scenarios, so the automated regression testing tool should do the same. With a trainable AI, various successful reusable test cases can combine to maximize productivity. The AI already recognizes what constitutes a successful case and will be faster at determining what passes and fails.

6. The reports generated by the AI program need to be quick, easy, and simple. They should list every relevant bit of information in a way that is easy to understand and review by the developer team. Also, everything should be scalable and flexible. This is best done with a combination of reports, screenshots, videos, and error logs.

Choosing the Right Tool for Visual Regression Testing

Just landing a tool for running automation testing is not a good business decision. Among multiple tools available, the ones that work the best for you and offer you good results should you be your first choice.

When considering what visual regression testing tool to use, website publishers should consider several factors:

Does the tool require programming skills to use?

This is fine if there is an entire team of developers and engineers because those skills are already present. But having a tool that does not require programming or coding skills is undoubtedly helpful for website publishers without a developer team.

Does the tool filter out positives from rendering differences that the human eye won’t notice?

If the tool points out every difference, then those differences need to be looked over again by a person to determine if they are a problem; there is ultimately no time saved.

Is the tool a complete solution package, or is it just an add-on to another tool?

There are visual testing tools that stand by themselves, enabling publishers and developers to create, run, and edit tests with them. But they only do visual testing, not regression testing, and need to be paired with a regression testing tool.

Is the tool open-source or commercial?

If it is open-source, what does support look like? What does the pricing scale look like if it is commercial, and is it workable for the publisher’s needs?

Visual Regression Testing and AI: What’s Next?

Visual regression testing A.K.A VRT compares screenshots of a user interface (UI) before and after changes are made. This helps ensure the UI stays the same, leading to a better user experience, reduced costs, and improved product quality.

AI is rapidly changing the landscape of VRT. AI-powered VRT tools can automate many of the tasks involved in VRT, such as taking screenshots, comparing screenshots, and identifying visual differences. This can save time and money, and it can also improve the accuracy and efficiency of VRT.

In addition, AI-powered VRT tools can detect more subtle changes to the UI, such as changes in font size or color. This can help ensure the UI is always consistent and visually appealing.

AI-powered VRT tools are also becoming more scalable to test large and complex UIs. This is important for organizations developing web and mobile applications with complex UIs.

Here are some of the trends in visual regression testing and AI that we can expect to see in the future:

  • Increased use of AI-powered VRT tools: AI-powered VRT tools are becoming more reasonable and easy to use, leading to increased adoption.
  • More sophisticated AI algorithms: AI algorithms for VRT are becoming more sophisticated, allowing them to detect more subtle UI changes and be more accurate.
  • Increased scalability of AI-powered VRT tools: AI-powered VRT tools are becoming more scalable, allowing them to test large and complex UIs.
  • Integration with other testing tools: AI-powered VRT tools are being integrated with other testing tools, such as unit and functional testing. This allows for a more comprehensive and integrated testing approach.
  • Automated VRT: VRT is becoming increasingly automated, allowing testers to focus on other tasks.

Overall, AI is having a major impact on visual regression testing. AI-powered VRT tools are making VRT more efficient, accurate, and scalable. This is leading to increased adoption of VRT by organizations of all sizes.

Testsigma’s Visual Regression Testing

Testsigma is a cloud-based automation program that runs regression tests, among other things. They use a simplified approach that enables anyone to run automated regression testing without requiring extensive coding or programming knowledge.

Testsigma’s features include:

  • Creating regression test plan with affected tests
  • Automated regression tests that auto-heal
  • Running multiple tests at the same time
  • Continuous integration to run tests after every new build
  • Comprehensive reports

Testsigma will allow teams to start automating from the design phase and run continuous tests throughout.

Testsigma’s Visual Regression Testing-1

Testsigma’s platform testing will be done for web and mobile applications. Writing automated tests is easy. Teams can easily create ‘step groups’ and use them throughout the testing process. It has a simple user interface and allows data sets to be modified for any condition. Additionally, data can be accessed globally and used for all test cases.

Testsigma’s Visual Regression Testing-2

The AI-Driven Approach

The AI-driven automation tool is perfect for continuous testing. It will suggest the use of affected or relevant tests, saving time. When there is a test failure, the AI identifies other difficulties that might have been affected and will try to auto-heal the tests to some extent. This will also save execution time and costs.

Another benefit of Testsigma is the cloud-based operations enable teams to run tests on any combination of browsers, devices, and operating systems. This will ensure that the app or site works on all browsers, all versions of browsers, and browsers run on different operating systems. It will also test for functionality on desktops, laptops, tablets, phones, and operating systems, including Windows, Mac, Android, iOS, and Linux. Not to mention, it will also incorporate resolution into the testing.

Testsigma - Create Test Plan

Teams can set test suites to run simultaneously, which decreases feedback time. Different environments can be run at the same time, making the testing time go down from days to mere hours. Executions can also be scheduled to run periodically in the background without manual start.

Other Testsigma features include: 

  • Local test runs
  • Drill-down test reports
  • Visual logs in the form of screenshots and videos
  • Text logs
  • Collaboration through email, Slack, and Teams
  • Various user and role management 
  • Reliable end-to-end regression tests for web and mobile 
  • Elimination of automation backlogs 

Ultimately, Testsigma provides continuous testing for an agile and ever-changing pipeline. Customers like Netgear, Hewlett Packard, and the American Psychological Association use it. Everyone from subject matter experts and quality assurance teams to developer teams and programmers can use Testsigma’s automated tests and write tests in basic English.

Conclusion

Visual regression testing is essential for anyone producing a product with a visual interface. Visual tests can be done manually or automated, usually through screenshot testing. While both have pros and cons, the advent of trainable AI has made regression testing automation a more viable option.

Employing a regression test tool will free up time for developers, subject matter experts, and website publishers to focus on other tasks. Testsigma offers a cloud-based option that anyone without programming or coding skills can use. Since the program learns and is self-healing, it is an ideal option for testing the breadth of visual combinations possible in today’s digital age.

Frequently Asked Questions (FAQs)

What is Visual Validation testing?

Visual Validation testing means checking for proper layout, spacing, font size, color, and overall aesthetic consistency. Visual validation testing ensures that the finished product appears and feels as intended and meets design requirements.

What are the Advantages of Visual Regression Testing?

Visual Regression testing helps to improve the UI layout of the application, website, or software after developers introduce new code changes in the background. Prime advantages of Visual Regression testing are fixing the visual errors before it reaches the end users and enhancing the overall customer experience for increased time-on-page and incoming traffic.

How to do Visual Regression Testing?

You can execute Visual Regression testing by generating test cases and running them through automated Visual testing tools, such as Testsigma, to compare the before-after screenshots.

Suggested Reading

Best Visual Layout Testing Tools

Automated Visual Testing on Testsigma 

Visual Testing | What It is and How to Get Started?

Regression Testing Guide for Modern Agile Teams

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