date-fns/date-fns

Tests and CI were inspected, not executed; no passing status or coverage percentage is established. Vitest discovers package projects, with separate core main and Temporal-oriented suites and package-specific isolation settings. Inspected tests exercise mutation guarantees, invalid input, parsing boundaries, context types, DST gaps, and historical offsets. CI describes browser, Node-version, time-zone, smoke, type, lint, and locale checks, but this bounded inspection does not establish exhaustive coverage.

• Root Vitest discovers pkgs/*; core main includes src/**/test.ts, temporarily includes test.tp.ts, and both use forks, disabled isolation, concurrent sequencing, and optional Chromium via Playwright.
  vitest.config.ts#L1-L7pkgs/core/vitest.config.ts#L7-L45
• addMonths tests assert timestamp support, input immutability, month-end clamping, pre-100 AD dates, invalid dates/amounts, UTCDate retention, and TZDate context inference.
  pkgs/core/src/addMonths/test.ts#L9-L49pkgs/core/src/addMonths/test.ts#L151-L180
• Formatting tests cover quote escaping and formatDate alias behavior; parsing tests cover leap-day bounds, mismatches, invalid references, trailing whitespace, and unescaped-letter errors.
  pkgs/core/src/format/test.ts#L45-L69pkgs/core/src/parse/test.ts#L2050-L2063pkgs/core/src/parse/test.ts#L2230-L2273
• TZ tests include src/**/tests.ts and test/**/*.test.ts; inspected edge cases assert spring-forward normalization and historical second-offset behavior, while UTC configuration enables isolation.
  pkgs/tz/vitest.config.ts#L3-L10pkgs/tz/test/edge/new-york.test.ts#L13-L36pkgs/tz/test/edge/historical.test.ts#L4-L26pkgs/utc/vitest.config.ts#L3-L10
• Push/PR workflows invoke core Node, browser, and time-zone tasks; Node tests name versions 22/24/25/26, and the zone runner launches Vitest with TZ and VITEST_MAX_WORKERS=1.
  .github/workflows/node_tests.yaml#L3-L15.github/workflows/browser_tests.yaml#L18-L22pkgs/core/scripts/test/node.sh#L7-L21pkgs/dev/src/test/tz.ts#L407-L413
• Smoke CI delegates to example tasks; quality CI invokes type checking, linting, and locale snapshots, whose renderer covers format/parse, distances, relative dates, and durations under TZ=utc.
  .github/workflows/smoke_tests.yaml#L14-L15.github/workflows/code_quality.yaml#L14-L21pkgs/core/mise.toml#L115-L123pkgs/core/scripts/build/localeSnapshots/index.ts#L24-L50
• The inspected docs tests assert export/module-node classification and repository-path conversion; its npm test script is a deliberate failure placeholder despite a Vitest tests.ts configuration, so that script is not a reliable docs-suite entrypoint.
  pkgs/docs/src/data/tests.ts#L1-L29pkgs/docs/vitest.config.ts#L3-L8pkgs/docs/package.json#L38-L40
• Coverage CI is workflow_dispatch-only with a TODO; addMonths DST cases are conditional on detected transitions, and inspected docs helper tests do not demonstrate Firebase publication/rollback verification. Tests and workflows were read, not run.
  .github/workflows/coverage.yaml#L3-L18pkgs/core/src/addMonths/test.ts#L52-L55pkgs/docs/src/data/tests.ts#L1-L29pkgs/docs/src/bin.ts#L34-L120