e2e-testing

E2E & Integration Testing

Verify whole flows through real interfaces. Complement unit tests; don't duplicate them.

Pick the tool by stack

Stack	Tool	Notes
Next.js / React web	Playwright (or Cypress)	Drive the browser; assert by role/text; test SSR + navigation + forms/actions
React Native	Detox or Maestro	Simulator/device flows; RN Testing Library for component-integration
Express / Fastify / NestJS API	Supertest / Pactum	Hit the real app instance; real/containerized DB
Service-to-service contracts	Pact	Consumer-driven contract tests
Any DB integration	Testcontainers	Ephemeral PostgreSQL/MongoDB, no mocking the DB
ASP.NET Core Web API (.NET)	WebApplicationFactory + xUnit	In-memory host + HttpClient; DB via Testcontainers for .NET; arm64-native on macOS
Avalonia desktop (XAML)	Appium (+ Avalonia.Headless for unit)	Drives the real window via the accessibility tree; macOS needs Accessibility permission
.NET web / Blazor UI	Playwright for .NET	Native Apple Silicon support

Principles

• Hermetic: each test seeds and tears down its own data; isolated DB state (transaction rollback or ephemeral container) so tests are parallel-safe and order-independent.
• Observable outcomes only: assert UI text/roles, HTTP status+body, or persisted DB state — never internals.
• No flake: wait on conditions, never fixed sleeps; stable selectors (data-testid/ARIA roles); retries only for genuinely async UI. Run new E2E twice to catch flakiness.
• Lean: cover critical journeys and highest-risk failures (auth, payments, data loss). Push exhaustive cases down to unit tests.
• CI-ready: tag E2E suites to run separately; document required containers/env vars.

See references/playwright-setup.md, references/api-e2e-setup.md, and references/dotnet-e2e-setup.md.