Visual Regression Testing (VRT) is a software testing process that ensures the visual appearance of a web page or app remains consistent over time, even after code updates. It’s used to detect unexpected changes in UI elements like colors, fonts, layouts, and images that could impact the user experience.

Example of Visual Regression Testing

Let's imagine a simple example of a website’s homepage. The homepage has a banner with a text overlay, a button, and a product image grid. The process of VRT in this scenario would look like this:

• Initial Baseline Setup:

1. Before making any changes to the code, take screenshots of key UI elements (e.g., banner, button, product images) as the baseline.
2. This baseline captures the current, visually correct state of the homepage.

• Run VRT After Code Updates:

1. Let’s say the development team modifies the CSS to add a new color scheme. This update could unintentionally affect button colors, font sizes, or the layout of images.
2. VRT tools capture new screenshots of the same UI elements after the changes.

• Compare Screenshots:

1. The VRT tool compares the new screenshots to the baseline. If there’s any difference, it highlights the changes for review. For example, if the button color unintentionally changed from blue to green, it would show this difference visually.

• Review Changes:

1. Developers or testers review the changes. If the change was intentional, they can update the baseline. If it’s a bug (e.g., unintended font change or button color change), they fix the issue.

• Update the Baseline:

1. Once the changes are verified and confirmed as intended, the baseline is updated to reflect the new visual state. This updated baseline will now be used for future tests.