Express.js
Testing an Express application written in TypeScript introduces both advantages and challenges. The advantages: your mocks can be type-checked, your request/response extensions are documented in the type system, and the compiler catches whole categories of test bugs before they run. The challenges: ts-jest configuration, typing custom middleware,
Express.js
Unit tests verify that your middleware logic is correct in isolation. Integration tests verify that your Express routes work correctly end-to-end: against a real database, with real request parsing, and producing real HTTP responses. This post covers the patterns that separate fragile integration tests from tests that actually
Express.js
Testing Express middleware is deceptively tricky. Basic Supertest tutorials show you how to fire a request and check the status code. But real middleware testing — the kind that catches actual bugs — requires understanding how middleware chains compose, how dependencies get injected, and how errors propagate through layers you didn'
Express.js
Error handling is the part of an Express app most developers test last — and it's the part that matters most when things go wrong in production. A well-tested error handling stack means your API never leaks stack traces to clients, always returns machine-readable error formats, and
Express.js
Authentication middleware is the most security-critical code in your Express application. A bug in your JWT validation could mean an attacker with an expired token can still access protected routes. A session middleware misconfiguration can leak one user's data to another. This post covers how to write