Visual Regression Testing Concepts
Understand pixel-diff and screenshot-based visual regression testing for catching CSS regressions.
What is Visual Regression Testing?
Visual regression testing (VRT) automatically detects unintended visual changes between code versions by comparing rendered screenshots pixel-by-pixel. It catches CSS regressions — layout shifts, color changes, broken spacing — that unit tests miss entirely.
How VRT Works
VRT takes baseline screenshots of components or pages, then takes new screenshots after code changes and compares them. Differences are highlighted in a diff image. Developers review diffs and either approve intentional changes or fix unintentional regressions.
All lessons in this course
- Visual Regression Testing Concepts
- Percy and Chromatic for Storybook
- CSS Unit Testing with Jest
- Accessibility Testing: color-contrast and focus