Test engineers may recall the fateful day when they confidently deployed the latest version of their application after their functional UI test suite gave the green light. But within hours, bug reports began detailing a mysterious UI element missing for some users but appearing for others. The culprit: a poorly written CSS media query invisible to your test suite.
In this article, you'll learn why visual tests are essential to an effective test suite and how they can complement your functional UI test to deliver even more confidence in your deployments.
What are Your Testing Goals?
Effective test suites ensure an application’s quality, functionality, and reliability. By executing a collection of test cases, you systematically identify and address potential issues before they reach production. And front-end testing usually involves assessing user interface elements, such as navigation, user input, and responsiveness.
Test suites should leverage multiple test types to assess every UI element and prevent bugs. These tests may include:
- Functional UI tests – These tests validate the application’s functionality by simulating user interactions. They usually focus on form submissions, data handling, and error handling.
- Accessibility tests – These tests ensure that accessibility elements, such as alt tags on images, are present.[Text Wrapping Break]
- Performance tests – These tests focus on the loading speed of page elements, which impacts usability.[Text Wrapping Break]
- Security tests – These tests validate an application’s security from the UI standpoint, covering issues like password rules.[Text Wrapping Break]
- Visual tests – These tests concentrate on the UI’s appearance, ensuring elements display correctly across different devices, screen sizes, and browsers. They help identify visual inconsistencies, such as misaligned elements, incorrect colors, or broken images.
Unfortunately, visual tests are often underutilized and overlooked in many test suites. Test engineers often rely exclusively on functional UI tests, which results in visual regressions that negatively impact the user experience. But ignoring visual tests opens the door to visual inconsistencies that are difficult to detect.
The Limits of Functional Tests
Functional tests focus on validating the functionality of an application. While they historically focused on unit and integration tests, functional testing has evolved to include testing user interfaces (UI). Using tools like Selenium, test engineers can validate that buttons, text fields, and other components produce the expected outputs.
As front-end UIs become increasingly complex, functional tests have run up against new limitations on their ability to conduct a thorough assessment. For instance, a seemingly innocuous change in an element’s ID can result in a test failure even if the UI looks the same. In other words, functional UI tests can be notoriously flaky.
On a broader level, functional UI tests are more focused on testing the behavior of the UI rather than its aesthetics. For instance, they may validate that an element appears in the DOM but not that it’s the right color or visible on screen. They also fail to assess the responsiveness or adaptability of a UI to different devices or screen sizes.
Let’s take a look at a concrete example:
Imagine you’re building a web application that displays data in a table. The table has alternating row colors to improve readability. The development team introduces a new feature enabling users to filter data in the table by a specific column.
A functional UI test might ensure that the filter button correctly filters the data and the row count matches the expected number. However, suppose the development team inadvertently introduces a bug that breaks the alternating row colors and shifts the text.
A visual test could quickly detect this bug by comparing two screenshots. If the entire table is one color, there’s a significant visual difference. By implementing visual tests, you could prevent this bug from reaching production and impacting readability.
Why Visual Tests are Critical
Visual design is critical to the user experience. Layout, typography, images, consistency, and other visual elements have a measurable effect on trust and conversion rates. At the same time, visual abnormalities, typographical errors, or broken links hurt a site’s credibility and impact conversion rates more than you might think.
As a result, visual tests are quickly becoming a critical complement to functional tests, addressing many functional UI test limitations when evaluating applications. By looking at actual UIs via image comparison or other methods, these tests can identify subtle inconsistencies across various devices, screen sizes, and resolutions.
The integration of visual tests with functional tests yields a comprehensive testing strategy that validates the correct functioning of UI components and ensures a visually pleasing and consistent experience. That way, you can accurately identify and fix potential issues before deploying potentially damaging changes to production.
But the challenge is finding the right visual testing tool. While many teams rely on manual visual testing, more and more tools make it easy to automate visual testing processes by programmatically comparing screenshots. However, the best tools strike an optimal balance between recognizing significant defects and flagging every single pixel.
How VisualTest Can Help
VisualTest is an AI-driven, automated visual testing platform that quickly confirms your app looks like what you – and your customers – expect. Unlike competing visual regression testing platforms, VisualTest has an AI-driven approach that tracks every visual change while ignoring false positives, helping your team be as productive as possible.
With a single code snippet, you can track changes on pages and elements of your application UI for every deployment. And integrations with Selenium and Cypress make it easy to implement VisualTest into your existing CI/CD workflows in the languages of your choice.
VisualTest makes it easy to compare differences between two versions within an intuitive user interface. Source: VisualTest
After implementing VisualTest with a test script, any user can log in and review or comment on visual changes. You can view side-by-side results and highlight changes to quickly find offending differences and flag them for a developer’s followup. No need to dive into the code to determine what’s passing and what’s not.
The Bottom Line
Many development teams rely on functional UI tests to validate forms, buttons, and other elements. But unfortunately, these tests almost always miss aesthetic changes that influence the user experience. The good news is that VisualTest improves test coverage and flags these problems with a single snippet of code.