api-testing
API Testing
Overview
API testing validates HTTP endpoints by sending requests and asserting responses, covering status codes, headers, body content, and error handling. Supertest provides a fluent chainable API for integration testing against Express, Fastify, and Hono apps without starting a real server. MSW (Mock Service Worker) v2 intercepts outgoing HTTP requests at the network level, enabling realistic mocking of external services in both Node.js tests and browser environments.
When to use: Integration tests for REST APIs, testing middleware pipelines, validating request/response contracts, mocking third-party APIs in tests, testing error handling and edge cases.
When NOT to use: Unit testing pure functions (use direct assertions), E2E browser testing (use Playwright/Cypress), load/performance testing (use k6/Artillery), testing static file serving.