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React Testing

React Testing Guide

Section titled “React Testing Guide”

Scope: React viewer toolkit (@scaryterry/pdfium/react).

Baseline commands

Section titled “Baseline commands”
  • pnpm test test/unit/react
  • pnpm test:react:stable
  • pnpm test:react:memory-regression

Use test:react:stable for routine local validation. It runs deterministic shards and is resilient to process-level memory pressure.

Use test:react:memory-regression when changing async orchestration, cache lifecycles, provider bootstrapping, or panel workflows.

Global teardown contract

Section titled “Global teardown contract”

React tests use test/react-setup.ts for shared teardown:

  • cleanup()
  • vi.clearAllMocks()
  • vi.restoreAllMocks()
  • vi.resetModules()
  • vi.unstubAllGlobals()
  • vi.unstubAllEnvs()

Avoid duplicating this in individual test files unless a file has additional, file-specific reset state.

Race testing standards

Section titled “Race testing standards”

For async lifecycle tests:

  • Prefer deterministic scheduling with vi.useFakeTimers() and vi.advanceTimersByTime(...).
  • Assert stale completion is ignored after:
    • document instance changes
    • page index changes
    • unmount/remount cycles
  • Cover both stale success and stale failure paths.

Test structure patterns

Section titled “Test structure patterns”
  • Hooks:
    • Use renderHookWithStores where store-backed hooks are under test.
    • Assert isLoading, error, and data transitions explicitly.
  • Panels/components:
    • Use explicit UI events + async flush in act(...).
    • Verify stale async results do not re-open alerts, overwrite result banners, or mutate selection on the wrong page.

Anti-patterns

Section titled “Anti-patterns”
  • Global mutable mocks without reset.
  • File-local afterEach(cleanup) duplication.
  • Time-dependent async tests that rely on real timers and wall-clock waits.

See also

Section titled “See also”