Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/dkmqflx/fastapi-best-practices-plugin/fastapi-testingnpx skills add dkmqflx/fastapi-best-practices-plugin --skill fastapi-testinggit clone --depth 1 https://github.com/dkmqflx/fastapi-best-practices-pluginWhat it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00060 | $0.00425 |
| Opus 5 | $0.00030 | $0.00212 |
| Sonnet 5 | $0.00012 | $0.00085 |
| Haiku 4.5 | $0.00006 | $0.00042 |
Grade A, and why
fastapi-testing scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
What it actually says
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 throughfastapi.testclient.TestClient(real HTTP, in-process)dependency-overrides(HIGH) — swap deps withapp.dependency_overrides, not monkeypatchasync-client(MEDIUM) — use httpxAsyncClient+ASGITransportfor 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 beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- yesterday First seen · 49 lines · 60 tokens per session scan A 381a45d2445e
fastapi-testing is a skill published in the GitHub repository dkmqflx/fastapi-best-practices-plugin (1 stars, last pushed 2mo ago), licensed MIT. It adds 60 tokens to every session and 425 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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