test(ui): full component test coverage — 48% → 97% statements, 226 tests

[Sam Gammon (sgammon)]

Summary

Test generation pass over @elide/ui: every previously untested component now has a behavior-focused jsdom suite. Coverage: 48% → 96.75% statements / 98.37% lines; 74 → 226 tests (34 files), all green. Also fixes a blind spot: the coverage include only counted src/components, so src/i18n and src/lib were invisible in reports — they're counted (and tested) now.

All tests follow the existing conventions (RTL role/name queries, userEvent, jest-dom): open/close and keyboard flows for the Base UI overlays, aria wiring (dialogs labelled by their titles, aria-current, aria-hidden separators), callback props, and real logic (theme persistence + OS preference, i18n deep-merge, keyed() stability, table-of-contents scroll-spy via a captured IntersectionObserver stub).

jsdom gaps are stubbed per test file, never in shared setup: PointerEvent, ResizeObserver, matchMedia, scrollIntoView, and an in-memory localStorage (Node's built-in localStorage shadows jsdom's and throws unless launched with --localstorage-file).

Remaining gaps (intentional)

• ScrollArea scrollbar/thumb — Base UI only mounts them after measuring real content overflow; jsdom has no layout. Render paths are covered; the browser-mode Storybook suite is the right home for the rest.
• mobile-nav branch coverage (~58%) — untested prop permutations (controlled open, section header variants); statements are at 100%.
• select.tsx (70%) — scroll-button/positioning code that needs layout.
• No visual-placement assertions anywhere (no layout in jsdom) — Chromatic owns those.

Pre-existing issue (not addressed here)

bunx tsc --noEmit fails on main in src/stories/CommandPalette.stories.tsx (2 × TS2322: story objects using render lack the required args) — shipped with #3, unrelated to this PR, left untouched to keep this tests-only. Trivial fix: add args: { groups: [] } (or make groups optional in meta args typing) to the two stories.

Test plan

• bun run test:coverage — 34 files / 226 tests pass; 96.75% stmts, 90.56% branch, 98.37% lines
• eslint src clean
• No component source touched — tests + coverage config only

🤖 Generated with Claude Code

[github-actions]

React Doctor found no new issues. 🎉

_{Reviewed by React Doctor for commit f9b3c70.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.72%. Comparing base (5eea68c) to head (f9b3c70).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@             Coverage Diff             @@
##             main       #5       +/-   ##
===========================================
+ Coverage   83.61%   97.72%   +14.11%     
===========================================
  Files          38       38               
  Lines         659      659               
  Branches      279      263       -16     
===========================================
+ Hits          551      644       +93     
+ Misses        108       15       -93     

Flag	Coverage Δ
ui-browser	97.72% <ø> (+14.11%)	⬆️
ui-unit	97.72% <ø> (+14.11%)	⬆️

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see 13 files with indirect coverage changes

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