How Visual Testing Takes Functional Testing to the Next Level

Lucas Fievet
January 30, 2023

Functional tests are important for verifying the functionality of a web application, but they have limitations. While functional tests check for proper data input, exception handling, and workflow, they can miss the bigger picture.

The browser rendering of a web app is crucial, but functional tests only examine the code, not the actual rendering. This can lead to the app appearing to pass functional tests, even if the pages aren't rendered properly.

To avoid this, it's important to clarify testing goals and expectations. Focusing solely on functional tests can lead to "functional test myopia," where the bigger picture is missed.

Consider a broader approach to testing, including checking the rendering of the app in a browser and examining the actual user experience.

What Conventional Functional Tests Miss

Functional end-to-end tests are designed to validate the functionality of a web application by simulating user interactions with the application. Despite their thoroughness, these tests can still miss certain types of bugs. For example, bugs related to the usability of the application, such as layout issues, font size and color contrast, are often missed by functional end-to-end tests. Performance-related bugs, such as slow loading times, high memory usage, or frequent crashes, are also often missed. Additionally, security bugs, such as vulnerabilities to SQL injection or cross-site scripting attacks, are not typically uncovered by functional end-to-end tests. To address these gaps, web applications require additional testing techniques, such as unit testing, performance testing, and security testing.

The Power of Visual Testing

Visual testing is a powerful technique in end-to-end testing that focuses on verifying the visual appearance and layout of a web application, rather than just individual elements and properties. By asserting the entire visual representation of a page or component, visual testing can provide a comprehensive view of how the application looks and behaves. This is particularly useful for catching visual bugs that may not be captured by asserting individual elements and properties, such as incorrect spacing, misaligned elements, or incorrect color schemes. Furthermore, visual testing can help identify inconsistencies or regressions across different browsers, devices, or screen sizes, ensuring a consistent user experience for all users. In summary, visual testing enhances the thoroughness and accuracy of end-to-end testing by supplementing the traditional approach of asserting individual elements and properties with a more comprehensive view of the application's visual appearance.

Why AI is Needed for Efficient Visual Testing

Pixel-wise comparison of screenshots is a traditional approach for visual testing, where screenshots of the application are compared pixel by pixel to detect any visual differences. However, this approach has several limitations. First, even minor changes in the appearance of the application, such as a font change or a slight shift in an element's position, can result in a significant number of differences in the screenshots and cause false failures in the test. Second,this approach requires manual effort to maintain a set of expected screenshots, which can be time-consuming and error prone. Finally, it can be challenging to handle dynamic content, such as responsive design, that may result in different appearances across different screen sizes or devices.

Artificial intelligence (AI) offers a solution to these limitations by using machine learning algorithms to identify the visual structure and layout of the application, rather than comparing pixel values. AI-based visual testing can detect subtle differences in the visual appearance, ignoring irrelevant changes, such as a slight shift in an element's position, and only reporting significant differences that affect the user experience. Additionally, AI-based visual testing can handle dynamic content, such as responsive design, by automatically adapting to changes in the layout and appearance. In summary, AI-based visual testing overcomes the limitations of pixel-wise comparison by providing a more flexible, accurate, and scalable approach for visual testing.

Visual Testing is The Future of Testing

In conclusion, visual testing is poised to play an increasingly important role in the software testing landscape as the focus on delivering high-quality user experiences continues to grow. The ability to validate the visual appearance and layout of web applications is critical for ensuring a consistent and seamless user experience. With the advancements in artificial intelligence, visual testing has evolved beyond simple pixel-wise comparison to a more sophisticated and effective approach for detecting visual bugs.

Astra, our testing platform, has the best visual testing capabilities, leveraging the latest AI technology to deliver unparalleled accuracy and efficiency. Astra's visual testing features provide developers with a comprehensive and flexible solution for validating the visual appearance of their applications, ensuring a high-quality user experience for all users. Whether you're testing a single page application or a complex web platform, Astra provides the tools you need to deliver the best possible experience for your users. With its cutting-edge technology and intuitive interface, Astra is the future of visual testing.

Example of visual differences found automatically with a single visual check

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