Testing

The web app has two test layers. Both run against mocked API data. Tests must never point at a real backend.

Unit / component tests (Vitest + React Testing Library + MSW)

Runner: Vitest with jsdom.
API mocking: MSW node server (test/msw/server.ts) with handlers in test/msw/handlers.ts. Unhandled requests throw (onUnhandledRequest: 'error'), so a test can never silently reach a live backend.
Render helper: test/render.tsx exposes renderWithProviders / render, which wrap components in the app providers (react-query with retries off, a mock SessionProvider). Import render, screen, userEvent from @/test/render.
Fixtures: test/fixtures.ts is the single source of truth for mocked API data, shared with the e2e layer.

Commands:

pnpm test          # run once
pnpm test:watch    # watch mode
pnpm coverage      # with coverage report

Place tests next to the code as *.test.tsx or under __tests__/.

End-to-end tests (Playwright)

Runner: Playwright, specs in e2e/.
The real Next dev server boots on port 3100 with a fixed NEXTAUTH_SECRET and a backend URL (localhost:3999) that nothing listens on.
e2e/mock-api.ts intercepts every /api/v1/** request and serves the shared fixtures, so no request can reach a real backend.
e2e/session.ts mints a valid NextAuth session cookie so tests run authenticated without the real login flow.

Commands:

pnpm test:e2e      # headless
pnpm test:e2e:ui   # interactive UI

First-time setup downloads the browser: pnpm exec playwright install chromium.

The rule

If a new screen calls a new endpoint, add a handler in test/msw/handlers.ts and a branch in e2e/mock-api.ts, both backed by a fixture in test/fixtures.ts. Never let a test hit the network.