Advanced · July 2, 2026 · 7 min

Visual regression testing catches the kind of bugs that unit tests miss: a button that moved, a broken layout, or text overlapping an image after a CSS change.

The basic pipeline

1. Capture a baseline screenshot of each key page
2. After every deployment, capture a new screenshot of the same pages
3. Run an image diff between the baseline and the new capture
4. Flag any difference above a defined threshold for manual review

Example integration

curl "https://yourapp.com/api/screenshot?url=https://staging.example.com&full_page=1&key=YOUR_API_KEY" -o after.png

Pair this with an open-source diffing library in your CI pipeline to automatically block deployments that introduce unexpected visual changes.