React Testing

React Testing

Goal

Validate new behavior without overengineering; run the smallest test set that proves the change works.

When to use

• Adding/changing React or UI behavior
• Writing or updating tests
• Deciding which tests to run
• Preparing a commit

Workflow

1. Identify the change scope (page/component/hook).
2. Ensure coverage:
   • If tests exist for that area, update them to cover the new behavior.
   • If no tests exist, add a minimal test for the new behavior (no snapshots).
3. Run scoped tests first (not the full suite).
4. If scoped tests pass, stop unless broader coverage is requested.
5. If unrelated failures show up in a full suite, report and stop; do not fix unless asked.
6. Before commit, re-run the scoped tests and ensure green.

Commands (Vitest)

• Single file: npx vitest run src/pages/runs/index.test.tsx
• Folder: npx vitest run src/pages/runs
• Test name: npx vitest run -t "hides tabs when browser is not ready"

Testing style

• Use React Testing Library.
• Assert on user-visible output and accessible roles/labels.
• Prefer getByRole/getByText; use *AllBy* only when multiples are expected.
• Avoid snapshots and brittle DOM structure checks.
• Avoid exact-copy assertions for non-contract UI text. Copy changes frequently and should not break tests.
• Prefer behavior/structure assertions (actions available, state transitions, section visibility, URL state).
• Allow exact-copy assertions only for contractual strings (legal/compliance copy, API/error contracts, critical security warnings).
• For expected error-path tests, spy on console.error and assert calls to keep test output clean while preserving coverage.

URL state coverage gate

If a change introduces URL-backed UI state (for example useSearchParams, location.search, or URLSearchParams), require at least one non-mocked behavior test that covers:

• query param -> derived state
• invalid query value -> fallback behavior
• state change action -> query param write/remove

Do not treat a page test that mocks the page hook as sufficient coverage for URL state logic.

Reporting

• Always state which tests ran and their result.
• If tests were not run, say why.

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