Integration Testing

When to use me

• Components have been unit tested and need to work together
• Testing API contracts between services
• Verifying database interactions work correctly
• Checking third-party service integrations
• Ensuring microservices communicate properly
• Validating data flows through the system

What I do

• Identify integration points between components
• Set up test environments with real or test databases
• Configure service connections and API endpoints
• Test data flow between integrated components
• Verify error handling across component boundaries
• Check contract compliance between services
• Validate end-to-end workflows without UI

Examples

# Run integration tests
npm run test:integration     # Node.js integration tests
pytest tests/integration/    # Python integration tests
go test -tags=integration    # Go integration tests

# Test specific integrations
npm run test:integration -- --grep "database"
pytest tests/integration/test_api_client.py

# Run with test containers for external services
docker-compose -f docker-compose.test.yml up --abort-on-container-exit

Output format

Integration Test Results:
──────────────────────────────
✅ API Service ↔ Database
  ✓ User data persists correctly
  ✓ Transaction rollback on failure

❌ Payment Service ↔ Banking API
  ✗ Authentication token refresh fails
  ✗ Currency conversion rate mismatch

⚠️ Email Service ↔ Queue
  ⚠️ Message retention period too short

Summary: 8 passed, 2 failed, 1 warning

Notes

• Integration tests are slower than unit tests
• Use test databases or in-memory databases
• Mock only external third-party services
• Test happy paths and error scenarios
• Clean up test data between tests
• Consider using test containers for external dependencies
• Focus on contract testing for microservices