Fastapi testing

Skill dkmqflx/fastapi-best-practices-plugin/plugins/fastapi-best-practices/skills/fastapi-testing

FastAPI testing best practices. Use when writing or reviewing tests for a FastAPI app — TestClient, dependency_overrides, async httpx clients. Triggers on TestClient, AsyncClient, ASGITransport, dependency_overrides, or pytest test files for FastAPI endpoints.From its SKILL.md

Install

npx -y skills add dkmqflx/fastapi-best-practices-plugin --skill fastapi-testing

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SKILL.md

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FastAPI Testing

Best practices for testing FastAPI applications, following the official testing docs (https://fastapi.tiangolo.com/tutorial/testing/). Covers exercising endpoints through real HTTP semantics via TestClient/AsyncClient, and swapping dependencies safely with dependency_overrides. Each rule pairs an antipattern with the idiomatic pytest pattern.

When to Apply

Reference these guidelines when:

Writing tests for FastAPI path operations
Swapping a dependency (DB session, auth, external client) for a test double
Writing async tests against an ASGI app without a running server
Reviewing or refactoring an existing FastAPI test suite

Rules

testclient (HIGH) — test endpoints through fastapi.testclient.TestClient (real HTTP, in-process)
dependency-overrides (HIGH) — swap deps with app.dependency_overrides, not monkeypatch
async-client (MEDIUM) — use httpx AsyncClient + ASGITransport for async tests

How to Use

Read the individual rule file for the detailed explanation and before/after example:

rules/testclient.md
rules/dependency-overrides.md
rules/async-client.md

Each rule file contains:

A short explanation of why it matters, tied to the official docs
An Incorrect example (the antipattern)
A Correct example (the official pattern)
A link to the relevant page on https://fastapi.tiangolo.com/

All examples follow the official FastAPI documentation and avoid deprecated APIs.

What ships with it: 3 files

4.0 KB alongside SKILL.md