Visual Regression Tests in WordPress Core

These tests make use of Jest and Puppeteer, with a setup very similar to that of the e2e tests, together with jest-image-snapshot for generating the visual diffs.

How to Run the Tests Locally

Check out trunk.
Run npm run test:visual to generate some base snapshots.
Check out the feature branch to be tested.
Run npm run test:visual again. If any tests fail, the diff images can be found in tests/visual-regression/specs/__image_snapshots__/__diff_output__.