Integration Testing Skill

This skill captures critical learnings from US-001 (birdmate project) where 3 integration bugs appeared in demo despite 272 passing unit tests. Covers CORS configuration, API contract validation, and build artifact hygiene.

CORS Development Configuration

Critical Pattern: Development CORS must accommodate dynamic port assignment

// ❌ WRONG - Single hardcoded origin
const CORS_ORIGIN = 'http://localhost:5173';

// ✅ CORRECT - Support port range
const CORS_ORIGINS = (process.env.CORS_ORIGIN || 
  'http://localhost:5173,http://localhost:5174,http://localhost:5175'
).split(',').map(s => s.trim());

app.use(cors({ origin: CORS_ORIGINS, credentials: true }));