How to Perform Visual Regression Testing?

In general, regression testing ensures that the modifications we make to our source code have no unintended consequences for our system. We are going for the same purpose with visual regression testing, but we are more concerned with the interface that is shown to our ultimate user than with the functionality of our system.

What essentially matters in the end, is what our user sees and interacts with. Basically, visual regression tests help us to determine how our consumers will react to changes by using screenshots and comparing the content of those pictures.

Visual Regression Testing: What Is It?

Regression testing ensures that any system modifications do not affect current functionality and/or code structure. There’s a reason regression tests are included in practically every software development test suite. It’s normal for developers to update or add code that accidentally breaks something that was previously operating well.

Visual Regression Testing follows the same reasoning as traditional regression testing, but it focuses on the software’s visual elements. In other words, it ensures that code changes do not affect the software’s visual interface in any way. Visual regression testing is often known as visual software testing. It is a quality assurance activity that verifies if the visual features of an application’s user interface seem suitable to the user. Another name for it is Visual Validation Testing.

The goal of this type of testing is to ensure that the application’s front end displays the correct data and information. It also verifies the arrangement and looks of each visual element on the user interface, as well as the whole user interface.

By comparing the screenshots that are taken before and after code changes, a visual regression test determines what the user would see once any code changes have been implemented. Visual regression testing is sometimes known as visual snapshot tests because of this.

How Does Visual Regression Testing Work?

To see whether any pixels have changed, visual tests produce, analyse, and compare browser snapshots. Visual disparities are the pixel differences, sometimes called pdiffs, perceptual diffs, CSS diffs, and UI diffs. Visual testing necessitates the following:

  • A test runner that lets you write and execute tests.
  • A framework for replicating the activities of the user in the browser/s.

Developers or testers write programming that mimics the actions of users, like typing text into a field, for example. They might insert orders to take a screenshot at strategic spots. Just when the test code is run for the very first time, a series of screenshots is taken to serve as a baseline against which all subsequent modifications will be measured.

The QA executes the test code in the background after establishing the baseline. A screenshot by the QA is taken whenever a change is detected. Each snapshot is compared to the baseline picture associated with that piece of the code and program. The test is regarded as failed in case there are variations between the photos.

A report is created automatically after the test code has been completed. The photos that have been found as altered from their baseline are then reviewed by a reviewer. Some testing software generates reports that show the variations between the baseline and final photos that were discovered after the test was completed.

Whether the picture changes are the result of problems, developers may repair them and repeat the test to see if the modifications were successful. Assume that other UI modifications result in discrepancies. Developers will have to go through the snapshot and update the baseline pictures against which future visual tests may be done.

How Can Visual Regression Testing Be Implemented?

It is significant to note that visual regression testing should be automated and integrated into the CI/CD cycle. This process will not only save time but will also decrease the risk of human mistakes and guarantee that the software’s aesthetics are preserved.

Create scenarios for testing and define what should be recorded in screenshots. When they should be taken throughout the test should also be considered. Be careful to incorporate a range of user interactions in these situations since this is what software will have to deal with in the real world.

Compare new screenshots (taken after code changes have been applied in software) with older screenshots using an automated visual testing method. 

One or more reviewers examine and report on whether the modifications made resulted in the desired outcomes or caused any disruptions.

If any bugs are exposed, they must be corrected or sent to the relevant teams to be fixed. Update the fresh screenshot as a baseline for any visual regression testing after that.

Use Case Scenario for Visual Bugs

Consider the case where a user accessed a web app and attempted to click a button but was unable to do so because an ad covered 3/4 of the button. The user feels upset, and he or she wonders how such an evident problem with the app’s user experience slipped by the creators. They may even uninstall the program since it deliberately stops them from benefiting from it.  This is a visual bug.

In essence, it is an inaccuracy that impacts a user’s visual experience when using the software. Users are most aware of visual issues since they are frequently the first thing they see when are using an application or visiting a website. 

Visual testing is crucial for finding and fixing issues. There are hundreds, if not thousands, of device-browser-operating-system combinations that carry out “code-to-pixel” talks in their own unique manner in the world we live in. This is why the same program on multiple machines might seem different (or be scrambled). Differences in screen sizes and resolutions must be taken into account as well, which is why responsive design should be a must in every development project.

Importance of Visual Regression Testing

No matter how well your program functions, it will be useless to customers unless it has a robust user interface and experience. These days, we speak about UX (User Experience) as well as UI (User Interface) (user experience). When it comes to providing a better user experience, visual testing is critical since a more attractive visual design is seen as more useable by the user.

In many ways, visual design influences the user experience.

For example,

  • Great visual designs aid in the development of trust and credibility.
  • Brand image is reinforced.
  • Legibility is affected.
  • On the screen, it creates a visual equilibrium.
  • Directs users to take action.
  • Persuades the eye to pay attention to particular things on the page.

Furthermore, since there are so many different operating systems, web browsers, screen resolutions, and devices available today, it is critical to guarantee that the UI looks well on all of them. Even a little UI flaw might result in lost revenue. Users may find visual bugs irritating and unpleasant, causing them discomfort.

Assume that you are in the banking industry and your clients have access to an online mobile banking application. Some of your customers report that when they wish to transfer money to someone’s account, they can’t locate the ‘Submit’ button on the page after entering all of the essential information, which is a frustrating experience for the clients.

When you look into the issue, you will discover that the submit button is hidden on a particular screen resolution for Android phones, which is why all clients using Android phones with that screen size couldn’t see it.

The application’s functionality was good in this situation, but users were unable to finish their planned tasks on the app due to visual problems. This example demonstrates how critical it is to test the application’s visual elements in every possible configuration before delivering it to clients.

Because it will have a direct influence on your brand, visual validation testing is strongly suggested in the following areas:

  • Apps for Mobile
  • Websites for mobile web/responsive web marketing
  • Systems for managing content
  • Airlines, travel, banking, and other consumer systems

Given its significance, businesses should devote substantial time and resources to visual testing. It will also assist you in spotting visual flaws in the early stages of the development lifecycle when used in conjunction with current developer tests.

Methods and Procedures For Visual Regression Testing

We often test the functioning of programs as developers or testers. We verify that the program is functioning correctly, either manually or via an automated tool. Such functionality testing is critical for ensuring the application’s seamless operation.

However, adding visual testing to this would considerably enhance the overall testing. As a result, this testing is often combined with functional testing.

To tackle the problems of visual testing of applications over a broad range of setups, numerous testing methodologies and procedures are available. Visual validation testing is also supported by a variety of technologies. Visual Regression Testing is often divided into two categories: code-based and configuration-based. These two methodologies are also used to classify visual testing tools.

It may be done either manually or automatically. It cannot be either manual or totally automated due to the difficulties involved. A mix of human and automated approaches is often recommended.

The three main visual testing methods that are often used are listed below.

Depending on their requirements, teams may pick from any of the following options:

  • Develop Dedicated Visual Tests: This is the best option since it offers you complete control over visual validation. You may also create tests with modest effort using this method. However, you will have to make the tests from scratch, which will take some time.
  • Add Visual Checkpoints to Existing Functional Tests: With this technique, you already have the tests in place to evaluate the application’s functionality; all you have to do now is add some visual checks in between them to validate the pages.

Of course, this technique reduces test coverage, but it’s a simple way to add visual tests while using existing functional testing code.

  • Add Implicit Visual Validation to Your Current Testing Framework: This technique is simple to create since it is only just a few lines of code. However, it has the drawback of being limited to generic validation in this scenario. Specific framework components cannot be validated.

Visual Regression Testing Tools

As previously stated, visual testing necessitates the use of a test runner to develop and execute tests. Test runners allow testers and developers to write code that mimics user behaviour. Assertions in each test define a condition that will either pass or fail. Organize tests into blocks and combine them into a single file to test a single module or software function.

Once the tests are created, interact with the browser using automation testing tools like Selenium or Cypress. They provide visual testing and enable the creation of web page screenshots.

Finally, a tool for controlling the testing process is required. Lambda Test is a platform where you may find visual discrepancies introduced with the latest release relating to icon size, padding, colour, layout, text, element position, and much more using smart picture to image comparison.

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