FastAPI
Unit tests verify individual functions. Integration tests verify that your application works when all the pieces are connected. For FastAPI applications, integration testing means running your endpoints against real databases, real caches, and real external services — not mocks. This is where you find the bugs that only appear in production:
FastAPI
FastAPI's dependency injection system is one of its most powerful features — and one of the most important to test correctly. When you override dependencies in tests, you control exactly what your endpoints receive, making tests fast, deterministic, and free of external side effects. This guide covers every pattern
FastAPI
Database testing is where most FastAPI applications get their testing strategy wrong. The common mistakes: using a shared test database that accumulates state, running migrations on every test, or — worst of all — hitting the production database in CI. This guide shows you how to test FastAPI applications backed by SQLAlchemy
FastAPI
Authentication bugs are the most expensive bugs you can ship. A missing authorization check or a JWT validation flaw can expose every user's data or let attackers elevate their privileges. This guide covers systematic testing of every auth pattern FastAPI supports, with enough depth to catch the edge
FastAPI
FastAPI is built on top of Starlette and runs on an ASGI server. Most of its interesting behavior — middleware, database calls, background tasks — happens asynchronously. Testing this code properly requires pytest-asyncio and a solid understanding of how async test infrastructure works. This guide goes beyond the basics to cover
Testing
FastAPI is async-native. Endpoint functions declared with async def run in an async context, and testing them requires an async test client and an async test runner. pytest-asyncio combined with httpx.AsyncClient gives you everything you need. This guide covers async endpoint testing, database integration, WebSocket testing, and
Testing
FastAPI's design makes testing unusually clean. Dependency injection isn't just an architectural pattern here — it's the mechanism that lets you swap real implementations for test doubles without monkey-patching. This tutorial covers TestClient, dependency overrides, database isolation, and async testing patterns you'll
HTMX
FastAPI is popular for APIs, but with Jinja2 templates it's a great HTMX backend too. Testing HTMX with FastAPI means using FastAPI's TestClient (Starlette-based) to send HX-Request headers and assert on HTML fragment responses, plus Playwright for browser-level interaction tests. Key Takeaways Use
Testing
You built a FastAPI service. The endpoints return the right data in your terminal. You open the docs at /docs and everything looks correct. You ship it.