Visual Regression Testing: What, Why and How

Software developers use visual regression testing to ensure that changes they make to a website or app don't result in unexpected visual changes or errors. Comparing screenshots of the website or application before and after changes are made allows you to spot any differences. 

With this aid, problems can be found that conventional testing techniques might not immediately pick up on. The maintenance of the quality and functionality of digital products requires the use of visual regression testing.

Visual regression testing, also known as User Interface testing, is a type of regression testing that delivers a quality product by ensuring a perfect user experience. It is a process of testing that validates that the changes made to an application do not affect the functionality and visual appearance of the application's user interface. 

Besides, it verifies if the visual elements align with expectations after the code changes are made to the website.

As a result, the visual regression test is more focused on the website's overall appearance, preventing any changes or issues that affect the application's visuals.

For visual regression testing, a wide range of regression testing tools are available for evaluating the visual quality aspect of the application by identifying visual bugs that hinder the application functionality. 

They improve overall product quality and mitigate the risk of rising issues while changes are made in the software. Using these automated regression tools has benefits such as:

• Save time and resources
• Keep maintenance low
• Set up testing 24/7
• Faster than manual testing

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How to Choose the Right Regression Testing Tool?

Since numerous regression tools are available, selecting the right tool can be difficult. So before picking a regression tool for your visual testing, ensure you understand your project needs and ask these questions to yourself.

How frequently will I have to Conduct the Visual Tests?

If it is occasional testing of your software, you can go with manual testing. On the other hand, if it is more often, automated testing tools are better.

What is the Range of Configuration?

This depends on the number of devices and browsers to run the tests. If there is a single configuration, you can use a tool that suffices the issue. However, you can pick a test tool that functions visual regression on a different configuration if it is a different range.

How Much Effort is Needed? 

Software with dynamic UI may have visual bugs, and there would be frequent changes. Therefore, team effort and advanced tools are necessary to meet the demands.

Can I Afford Paid Tool to Solve the Solution?

Paid regression tools have more advanced features than free ones. They provide a plug-and-play integration for a seamless consumer experience.

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What are The Visual Regression Testing Tools?

The Regression test tool's main function is to analyze each screenshot captured at different points to detect the visual differences in the application. They identify the visual bugs and ensure the existing software's functionality are not affected by the new software changes. 

In short, the visual regression test tool aims to verify the user interface change followed by the software's source code modification. So here are some significant visual regression test tools on the basis:

1) Paid Automation Visual Regression Tools: 

As mentioned earlier, paid tools to have more functions and features than free regression tools. They offer you to upload the screenshots to their content delivery network and provide highly scalable and fast delivery required for the testing. Some of the top paid automated visual testing tools include:

Kabiton: Kabiton is a mobile testing platform that provides the most comprehensive mobile visual validation solutions. It has a scriptless automation visual testing solution that offers mobile visual validation and Visual UX testing solutions. 

Besides, they identify visual bugs and optimize mobile UI and UX. Moreover, it captures visual and functional issues that would have otherwise gone unnoticed. Their essential features include Scriptless test automation, Visual and text affirmations, JIRA integration, Scriptless Appium exports, Local device connections, and Advanced and reporting analytics.

Applitools: It offers a cloud-based visual UI testing solution for web, mobile, and desktop apps. It confirms the USB dual output across different operating systems and trousers. Moreover, they support Full-page screenshots, page layout matching, and cross-browser testing. 

This tool can integrate with DevOps processes and easily create visual test cases or get into your CI/CD pipeline. Additionally, it also offers you the ability to create custom visual reports for easy readability. It supports all major automated testing frameworks, including Selenium IDE, Selenium, Cypress, WebdriverIO, etc.

Visual Regression Testing Percy: Percy is an automated visual test tool that conducts visual validation tests automatically. It helps you to create, build, and deploy software. Moreover, they support responsive visual testing, visual regression testing, and cross-browser testing. 

Besides, their pixel-by-pixel differentiation technology detects even minor changes in your UI and enables you to test UI across all screen widths. The snapshot stabilization technology decreases the possibility of false positives.

Lambda Test: The Lambda test is a sophisticated visual testing tool that allows teams to compare and contrast multiple picture layouts to identify discrepancies. Its image-to-image comparison technology enables one to find minimal visual bugs easily by simply uploading screenshots and running the test.

CrossBrowser Testing: CrossBrowser Testing's visual testing shows that bugs don't slip to your customers. It offers automated screenshot features that make every mobile layout excellent. It is also empowering to perform device testing for visual testing on the cloud platform. It fits into your CI process by integrating with tools like Jenkins and GitHub.

Chromatic: Chromatic helps in making UI components consistent. It uses pixel-perfect screenshots of real code, styling, and assets. Every commitment to the repository is automatically tested for visual changes in the cloud. It can also be integrated with GitHub, CircleCI, BitBucket, Travis, Jenkins, etc.

2) Open-source Visual Regression Test Tools: 

With open-source visual regression tools, you can maybe find a project that matches your requirements and enable you to fulfill your purposes regarding visual regression testing. Given below are some top open-source visual regression tools:

BackstopJS:  BackstopJS is a prominent visual regression open source project, well strengthened, very detailed, and flexible to be utilized in various scopes of JS web projects. It provides screens with Chrome Headless and deals with interactions with Puppeteer scripts. 

It develops an HTML report with the discrepancies found and furnishes us with its Docker Image to run the tests in CI.

Loki: Loki is very manageable to use tools for projects that consume Storybook and further runs with Chrome Headless. If you already utilize Storybook in your project, it is only plug-and-play. It has extremely detailed documentation and also possesses easy CI integration.

Cypress Visual Regression: Cypress is a very important testing framework that enables you to effortlessly add visual regression testing with this tool, incorporating it with your existing tests.

PhantomCSS: Phantom CSS is an open-source regression tool that combines three tools- PhantomJS, CasperJS, and ResembleJS. PhantomJS or SlimerJSare headless browsers that allow access to web pages and capture photos.

CasperJS is a tool that enables you to navigate and interact with the pages rendered by the browser. With it, we can simulate clicks, fill out forms, and perform JavaScript functions. ResembleJS is a library that compares images.

3) Angular Visual Regression Testing:

Angular Visual Regression Testing ensures the integrity of your web application's user interface by systematically detecting and highlighting any unintended visual changes, helping maintain a consistent and visually appealing user experience.

Protractor: Protractor is an end-to-end framework for AngularJS applications and Angular-based applications. It enables you to make robots interact with your application. Besides, it automates end-user actions within the browsers since it is built on WebDriverJS.

Conclusion

You can choose the right visual regression tool depending on your project needs, budget, and outcome. Besides, various automated visual regression tools are available in the market. They play a crucial role in developing dynamic software applications that run smoothly on different configurations, including devices, operating systems, and browsers. 

Frequently Asked Question Of Visual Regression Testing 

1) What is Regression Testing and Its Type?

Regression testing is software testing that ensures the changes made in the software do not affect the functionality of the existing software application. It is a verification process that detects errors or bugs in the software and checks the new changes do not create defects that can affect the existing functionality. 

Besides, it is significant when there are changes and improvements in the developed software. As a result, there are different types of regression testing to ensure the functionality of the software: 

• corrective 
• retest 
• progressive 
• selective
• complete
• partial 
• unit 

2) How Can You Ensure that Regression Testing is Effective?

To ensure effective regression testing, you can first collect all the test cases, monitor changes, and evaluate those by understanding their impact on different components. As a result, you can regularly screen test cases and analyze how changes have impacted the functionality of the existing software. 

You can also identify the problematic area of the test case to remove the bugs. Moreover, you can maintain a regression test suite by categorizing test cases based on their reusability and testability.

3) What are the Three Techniques of Regression Testing?

The three techniques of regression testing include:

• Retesting everything
• Regression Test Selection
• Prioritization of Test cases.

4) What is the Best Time to Perform Regression Testing?

The best time to perform regression testing is whenever there is a modification in the source code of your applications. For example, when you introduce a new feature or functionality to your existing software or fix a visual bug or errors in the software. As a result, it helps developers to identify defects on time and avoid software failures.