css-component-testing

# CSS Component Testing Test public CSS behavior in a browser. Prefer computed styles and bounding boxes for stable assertions; use screenshots only for targeted visual regressions. ## What To Test - Token-driven styles resolve through CSS custom properties. - Public states work: hover, focus, selected, disabled, open, dragging. - Layout dimensions and positioning stay within expected bounds. - Light and dark `color-scheme` paths do not throw or hide content. - Nested selectors compile through the existing build pipeline. ## Test Pattern 1. Mount the smallest fixture that exposes the CSS behavior. 2. Wait for custom elements and fonts/layout to settle. 3. Read `getComputedStyle`, `getBoundingClientRect`, or public attributes/classes. 4. Assert behavior, not implementation details, unless debugging a specific regression. ## Avoid - Broad screenshot snapshots for every component. - Assertions tied to browser antialiasing or exact subpixel layout unless necessary. - Testing private class names when a public attribute/state can be asserted instead.