CSS Unit Testing with Jest
Test CSS-in-JS outputs and snapshot styled components using Jest and related matchers.
Why Test CSS with Jest?
CSS unit testing verifies computed styles, class application, and layout behavior programmatically. It catches CSS logic regressions (wrong class applied, missing modifier) without requiring a browser screenshot or manual visual inspection.
JSDOM and CSS Support
Jest uses JSDOM by default, which has limited CSS support — it does not compute layout or evaluate complex selectors. For basic class presence and inline style testing JSDOM is sufficient; for computed property testing, use jest-environment-jsdom with CSS module mocks.