Api Testing Patterns

This is the pattern library you reach for when building API tests that actually prevent breaking changes in production. It covers consumer-driven contract testing with Pact, comprehensive REST and GraphQL validation, and the critical scenarios teams often miss: expired tokens, race conditions on shared resources, idempotency key handling. The quick reference table breaking down contract versus component versus integration testing is genuinely useful for figuring out what layer you should be testing at. Four coordinated agents will validate contracts against OpenAPI specs, generate test suites, run load tests, and scan for security issues. The code examples are production-ready, especially the concurrency test that verifies inventory doesn't oversell when hit with parallel requests.