qain docs

Usage documentation for qain — semantic style-regression testing for Chromium. For what the output looks like before reading anything, see the live demo, regenerated by CI from examples/.

Guides

• Getting started — install, capture your first snapshot, read your first diff.
• CLI reference — every command and flag: snap, diff, view, shot.
• Recipes — snapshot a dev server, scope to one element, point at a Storybook story, extract computed styles as data, gate CI and coding agents on the exit code.
• GitHub Action — a sticky PR comment with the semantic diff and before/after/diff screenshots whenever a committed baseline changes.
• Snapshot & diff format — what is inside the JSON the CLI reads and writes.
• Using @qain/core as a library — capture and diff from your own code, with Playwright, Puppeteer, or a raw CDP socket.

Test-runner integrations

Each integration is documented in its package README:

• @qain/playwright — toMatchStyleSnapshot for Playwright tests.
• @qain/vitest — the same matcher for Vitest browser mode; component VRT without booting Storybook.
• @qain/storybook — matchStyleSnapshot for the Storybook test runner; every story becomes a style test.

Design

The main README covers the ideas: why the diff stays quiet, how rule attribution works, what replay does, and what qain deliberately does not do.