Best Practices for Visual Testing

Visual testing is a crucial component of modern software development. It ensures that applications function correctly and present a consistent and appealing interface to users.

Many high-performing organizations across various industries, including software, financial services, and healthcare, have adopted visual testing to enhance their quality assurance processes.

This article will share some best practices of visual testing that you can implement.

What is Visual Testing?

Visual Testing, sometimes called visual UI testing, verifies that the software user interface (UI) appears correctly to all users. Essentially, visual tests check that each element on a web page appears in the right shape, size, and position. It also checks that these elements appear and function correctly on a variety of devices and browsers. In other words, visual testing factors in how multiple environments, screen sizes, OSes, and other variables will affect software.

Visual tests generate, analyze, and compare browser snapshots to detect if any pixels have changed. These pixel differences are called visual diffs (sometimes called perceptual diffs, pdiffs, CSS diffs, UI diffs).

What can Teams Achieve With Visual Testing

Given below is a list of things that teams can achieve with visual testing

• UI/UX Consistency Across Devices and Screens: Automated visual testing ensures the user interface remains stable amid changes like CSS updates, covering all UI elements across various browsers and screen sizes for comprehensive reliability.
• Navigating QA Blind Spots with Visual Regression Testing: Visual regression testing identifies visual bugs that functional and manual testing may miss. It compares screenshots across devices and resolutions to help QA teams spot discrepancies.
• Enhanced Productivity and Scalability: Automated visual testing delivers faster, more precise results while being cost-effective. Its scalability benefits developers, designers, and marketers by streamlining design verification and updates.
• Confidence in Code Refactoring: Visual testing reduces uncertainty during coding by automating bug detection, allowing for confident deployments with assurance that the app appears correctly across all browsers and screens.

Benefits of Visual Testing

Here are some key reasons why you should perform visual testing:

• Increased Efficiency with Automated Testing: Automated visual testing reduces the time and effort needed for manual testing, minimizing the risk of human error and ensuring comprehensive coverage of all scenarios in complex applications.
• Enhanced Visual Accuracy: By incorporating visual testing alongside functional tests, organizations can identify crucial visual discrepancies that impact user experience, ensuring elements like alignment, pixel accuracy, and responsive design are consistently evaluated.
• Streamlined Responsive Design Verification: Automated visual testing simplifies maintaining a uniform visual appearance across various devices and screen sizes, making it easier to adapt to the growing diversity of platforms.

Strategies for Visual Testing

Below are the key strategies for visual testing:

• Automation: Implementing test automation streamlines UI reviews, reducing time and effort while minimizing human error.
• Parallelization: Running automated tests parallelly across various configurations accelerates the testing process without sacrificing quality.
• Testing on Real Devices: Utilizing real devices, particularly through cloud-based platforms, ensures accurate visual testing across a wide array of OS and device combinations.
• Testing on Mobile Browsers: Conducting visual tests on mobile browsers is essential, given that over half of global web traffic comes from mobile devices.
• Coverage: Ensuring comprehensive testing coverage is critical to prevent revenue loss and guarantee optimal user experience across all devices and screen resolutions.

Best Practices for Visual Testing

Here are the best practices for Visual Testing:

• Perform system tests first: Don’t run visual tests before ensuring that every feature works exactly as intended. Invest maximum effort at the unit tests level so that later-stage tests (usually covering larger sections of the software) do not return significant issues – which inevitably take more effort to resolve.
  When in doubt about what order tests should be structured in, just refer to the testing pyramid. Tests should go in the following order: Unit Tests > Integration Tests > UI Tests
• Create small specs: Creating smaller specs is helpful because if an issue does emerge, it is much easier to detect. Specs with greater detail can not only lead to more errors (because they tend to cover larger sections of software) but also make debugging more difficult because more code needs to be investigated.
  It is best to limit each spec to the layout details of a single web element. Don’t create one spec for one website page. Each webpage comprises multiple web elements, and its corresponding spec will require enormous amounts of detail. Instead, craft small specs for each element that accurately tests them, and when put together, fully defines the webpage.
• Use dedicated specs: There are millions of elements on every single website and app. To run visual tests that take each of them into account, testers will have to use structured, dedicated specs to ensure that they do not miss any visual elements.
  Try using the following blueprint for visual tests:
  Header > Main Section > Scroll Section 1 > Scroll Section 2 > Footer
  Create a full spec for the page by using the above as the main sections. Then, start running tests for each section.
  Take the example of the header. It may look something like this:
  Automated visual tests should be programmed to test each element and gauge whether they align with the baseline requirements in terms of pixels.
• Use relevant logs: It is easy to assume that visual UI testing bugs can be identified simply by looking at the images of the bug-ridden interface and comparing them to baseline images.
  This isn’t always applicable. Sometimes, the discrepancy is so minuscule that it can be detected in terms of pixel differences but not with the human eye. In such cases, the tester needs more data to detect the cause of the discrepancy.
  Logs related to the software test help provide the data testers need. Visual logs with timestamps can be helpful with this. But what’s necessary is some kind of key identifier that can be linked to the visual error. Otherwise, testers have to comb through all the code and images to figure out the issue.Consider using a tool that would help with logging. For instance, Percy by BrowserStack grabs screenshots, identifies visual changes, and informs the testing team of all changes.
• Use Baseline Images Effectively: Establish reliable baseline images representing the expected UI. These images serve as a reference point for future visual tests, helping to identify unintended changes accurately.
• Define Critical Elements to Test: Identify and prioritize the key components of your UI that significantly impact user experience. Focus testing efforts on these critical elements to ensure high-quality visuals where they matter most.
• Automate Screenshots and Compare Changes: Implement automated screenshot capture for consistent comparison against baseline images. This process helps detect visual discrepancies quickly, streamlining the identification of issues across different screens and resolutions.
• Review and Update Visual Tests Regularly: Regularly audit and refresh visual tests to align with design changes and updates. This practice ensures that tests remain relevant and effective in catching new visual bugs or discrepancies as the application evolves.
• Start with the basics: When verifying a web element, start with the following questions:
  • Is the element of the right size?
  • Is the element placed within a parent element, if it is supposed to be so?
  • Is the element inside another element, if it is supposed to be so?
  • Is the element located on the top/bottom/right/left of another element?
  • Are all elements aligned accurately relative to each other and in the broader context of the webpage structure?

Obviously, like most forms of testing, visual testing should be ideally automated. This requires the right tool: one which manages the test process and generates reports for manual testers to study and approve/disapprove.

Talk to an Expert

Visual Testing with BrowserStack

Percy by BrowserStack is one of the best-known tools for automating visual testing. It captures screenshots, compares them against the baseline images, and highlights visual changes. With increased visual coverage, teams can deploy code changes with confidence with every commit.

With Percy, testers can increase visual coverage across the entire UI and eliminate the risk of shipping visual bugs. They can avoid false positives and get quick, deterministic results with reliable regression testing. They can release software faster with DOM snapshotting and advanced parallelization capabilities designed to execute complex test suites at scale.

Percy’s SDKs enable users to easily install them and add snapshots. The visual testing tool also integrates with CI/CD pipelines and source code management systems to add visual tests to each code commit. As mentioned before, once tests are initiated, Percy takes screenshots and identified visual changes. Then, testers can easily review visual diffs to decide if the changes are legitimate or require fixing.

By incorporating the core practices detailed above, visual testing can be streamlined for greater speed, accuracy, and efficiency. Couple them with the right tools to deliver visually perfect applications quickly and consistently.

Try Automated Visual Testing for Free