api-contract-testing

# API Contract Testing Verify that APIs honor their contracts between consumers and providers without requiring full integration tests. ## Key Concepts | Term | Definition | |------|------------| | Consumer | Service that calls an API | | Provider | Service that exposes an API | | Contract | Agreed request/response format | | Pact | Consumer-driven contract testing tool | | Schema | Structure definition (OpenAPI, JSON Schema) | | Broker | Central repository for contracts | ## Pact Consumer Test (TypeScript) ```typescript import { PactV3, MatchersV3 } from '@pact-foundation/pact'; const provider = new PactV3({ consumer: 'OrderService', provider: 'UserService' }); describe('User API Contract', () => { it('returns user by ID', async () => { await provider .given('user 123 exists') .uponReceiving('a request for user 123') .withRequest({ method: 'GET', path: '/users/123' }) .willRespondWith({ status: 200, body: MatchersV3.like({ id: '123', name: MatchersV3.string('John'), email: MatchersV3.email('john@example.com') }) }) .executeTest(async (mockServer) => { const response = await fetch(`${mockServer.url}/users/123`); expect(response.status).toBe(200); }); }); it('returns 404 for non-existent user', async () => { await provider .given('user does not exist') .uponReceiving('a request for non-existent user') .withRequest({ method:...