Assuring the quality and dependability of web apps is crucial in the fast-paced world of software development. Ensuring codebase updates do not generate unintentional visual flaws, and if detected, any developers frequently modify them. This is because it may lead to visual bugs in the application and impact user experience. Visual regression testing is an essential procedure that aids developers in identifying and resolving visual differences between several iterations of a web application. We will go further into the world of visual regression testing in this thorough tutorial, studying its definition, advantages, tactics for implementation, and well-liked technologies.
What is Visual Regression Testing?
A web application or user interface’s visual look across several versions or states is compared and validated using the software testing approach known as visual regression testing. Visual regression testing’s major goal is to find any unintended visual changes or discrepancies that may have been introduced by coding changes, CSS updates, or other changes made during the development or maintenance process.
Visual regression testing especially targets the graphical elements of the user interface, as opposed to conventional functional testing, which focuses on validating the functionality and behaviour of an application. It seeks to guarantee that the program’s visual components, layout, and design stay constant and fault-free throughout the development lifecycle.
Taking screenshots of a web application in a reference or baseline state is necessary in the visual regression testing process. These reference pictures show how the program should look visually. New screenshots are taken for each release or upgrade as the codebase or user interface is altered. To spot variations, the visual regression testing tool assesses these fresh screenshots against the original examples.
Key Components Of Visual Regression Testing
Several crucial elements of visual regression testing come together to guarantee the efficacy and accuracy of the testing procedure. These elements aid in the accurate detection of visual anomalies and the avoidance of unintentional visual defects. We’ll examine the essential elements of visual regression testing now:
The baseline image serves as the reference point for visual regression testing. The application’s user interface is in its “known good” condition, as it was photographed during a stable application version. To detect any visual changes, later test runs will contrast the application’s current version with this baseline image.
Screenshots taken during visual regression tests of the most recent application version are known as “test images.” These photos are contrasted with the reference image to find any visual discrepancies. Automated testing technologies that mimic user interactions or run particular test scenarios are typically used to take test photos.
Visual Comparison Tool
The visual comparison tool, which is a crucial element in making the actual comparison between the baseline and test photos, is used. It examines the pixel-level variations between the two photos to find visual changes. To minimise false positives, the tool should be able to manage dynamic content and offer choices for masking or ignoring particular sections.
Test Automation Framework
Visual regression testing is most productive when included in a test automation framework. The preparation, execution, and reporting of tests, including visual regression tests, are handled by the automation framework. It makes combining visual and functional tests possible, assuring thorough coverage seamlessly.
Continuous Integration (CI) Integration
Visual regression testing must be integrated into the continuous integration (CI) pipeline to maintain a quick development cycle and discover visual errors early. Visual tests are automatically launched with each code commit thanks to CI integration, giving quick feedback on visual changes.
Managing Dynamic Content
Dynamic content, which changes in response to user interactions or real-time updates, is frequently used in web applications. Correct handling of dynamic content is essential for precise visual regression testing. The test accuracy can be increased by utilising strategies like clever masking or removing dynamic aspects that aren’t relevant.
Baseline photos and other test artefacts must be stored in version control for collaboration and traceability. Teams may track how the application’s visual look has changed with version control and return to earlier baseline pictures if necessary.
It’s critical to carry out visual regression testing across various browsers because different browsers may render web applications differently. Cross-browser testing helps identify browser-specific visual problems and ensures a consistent user experience across all platforms.
Reporting and analysis
The method of visual regression testing ought to produce thorough, useful reports. The reports must identify visual changes and include context details, such as the page URL, component, or element. This makes it possible for developers to find and fix aesthetic flaws rapidly.
Implementing Visual Regression Testing
Implementing visual regression testing can greatly enhance the quality and stability of a web application. By comparing screenshots of the application across different versions, any unintended visual changes or bugs can be quickly identified and addressed, ensuring a seamless user experience.
- Selecting the Appropriate Testing Method
Visual regression testing can be done in various ways, each with advantages and limits. There are three main approaches:
Screenshots of the entire page
This method involves screenshots of the full website during the reference phase. Another screenshot is taken during further testing, and the tool compares it with the reference image to find visual differences. The straightforward implementation of this approach could lead to false positives due to slight dynamic content changes.
Comparisons at the Element-Level
Instead of comparing the entire website with this method, certain parts like buttons or headers are the focus. This offers more specific insights into aesthetic inconsistencies but necessitates careful element selection.
Comparisons of DOM Snapshots
DOM snapshot comparisons entail taking a snapshot of a page’s DOM structure and comparing it to earlier iterations. Although it might be more difficult to implement, this strategy has the potential to be quite accurate.
- Selecting the Proper Tool
Visual regression testing can be facilitated by several tools. Typical examples include:
Google created the potent Node.js library puppeteer. It offers a high-level API for managing headless Chrome or Chromium instances, making it simple to take screenshots and compare them.
A visual regression testing tool based on Puppeteer is called BackstopJS. It enables developers to design test scenarios and produce reports for visual variations across different application versions.
Popular end-to-end testing framework Cypress has features for visual regression testing. It allows developers to create tests and graphically contrast various application states.
Selenium is a popular automation testing framework that may be enhanced with plugins or other libraries to carry out visual regression testing.
- Establishing a Stable Baseline
A solid baseline is necessary to provide reliable visual regression testing. The baseline acts as the comparison point for all subsequent testing. The application’s visually stable version should be used as the first baseline.
- Dealing with Dynamic Content
Dynamic information, such as user-generated data or in-the-moment updates, is frequently used in web applications. Dynamic content should be managed carefully to do efficient visual regression testing. Accuracy can be increased by ignoring unimportant dynamic aspects or applying masking techniques.
- Using continuous integration to integrate
Visual regression testing should be integrated into the continuous integration (CI) workflow to fully reap its benefits. With each code commit, automated visual regression tests are conducted to ensure rapid feedback on visual changes and preserve visual consistency.
Best Practices for Visual Regression Testing
Maintaining the visual integrity of online applications can benefit from the technique of visual regression testing. Developers should adhere to best practices that enhance accuracy, dependability, and efficiency to guarantee efficacy. Here are a few suggestions for visual regression testing best practices:
- Create a Stable Baseline
As the foundation, use a version of the program that is stable and visually appealing. The reference image ought to depict how the program is supposed to look. Store the baseline image under version control to make subsequent test runs easier to compare and reference.
- Regular testing
Visual regression testing should be done frequently, ideally after each significant modification or feature addition. Regular testing aids in the early detection of visual flaws and guards against adding regressions to the software.
- Automate testing
Use automated testing frameworks and tools to perform visual regression testing. Compared to manual testing, automation ensures test consistency and repeatability and saves time. You may incorporate several visual regression testing tools into your CI/CD pipeline.
- Integrate with CI/CD
Visual regression testing should be integrated into your workflow for continuous integration and deployment (CI/CD). Every time a code contribution is made, tests are immediately run to ensure quick feedback on visual changes and keep bugs from making it into production.
- Control Test Environments
Ensure that test environments closely reflect the production environment. This entails utilizing the same browsers, screen resolutions, and operating systems for reliable results. False positives and negatives in testing environments are reduced through consistency.
- Handle Dynamic Content
Web applications frequently contain dynamic content that evolves. When performing visual regression testing, adequately handle dynamic content. To account for such changes, use dynamic baseline creation, smart masking, and dynamic element exclusion.
- Maintain Version Control
Store all test artifacts in version control, including baseline images and test results. This records past aesthetic modifications and makes collaborating easier for team members.
- Perform Cross-Browser Testing
Cross-browser testing should be done to ensure visual coherence across many platforms by testing the program on various browsers and devices. Cross-browser testing allows spotting browser-specific visual problems that could otherwise go unreported. You can leverage cross browser testing and visual testing with Cloud-based platforms like LambdaTest. It is an AI-powered test orchestration and execution platform that offers AI-backed visual UI testing cloud. It allows you to run automation testing and manual testing in 3000+ real browsers, devices and OS combinations.
You can perform visual testing using LambdaTest and ensure the functioning of applications across diverse platforms. LambdaTest has led the way in providing effortless one-click visual regression testing for detecting UI regression bugs. Through intelligent testing capabilities, you can conduct sophisticated image-to-image comparisons, swiftly pinpointing visual inconsistencies encompassing text, layout, color, size, padding, element positioning, and more. What’s more, the implementation of parallel testing significantly minimizes test execution duration. The most exciting facet is the seamless integration into your entire CI/CD technology stack!
- Implement Visual Testing in E2E Tests
Visual testing should be used in E2E tests: Regression testing for visuals should be integrated into your end-to-end (E2E) test suite. With this method, you may mix functional and visual testing for a more thorough application testing strategy.
Visual regression testing is a crucial technique for creating web applications. It allows teams to create a professional and uniform user experience while eliminating unintentional visual flaws. Developers may easily incorporate visual regression testing into their development process and produce high-quality web applications that delight users with their consistent appearance by following the implementation methodologies and best practices described in this guide.