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 skills add chen3feng/agent-skills --skill test-layout-evolutiongit clone --depth 1 https://github.com/chen3feng/agent-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/chen3feng/agent-skills/test-layout-evolution)<a href="https://agentmods.dev/skills/chen3feng/agent-skills/test-layout-evolution"><img src="https://agentmods.dev/badge/skills/chen3feng/agent-skills/test-layout-evolution/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/chen3feng/agent-skills/test-layout-evolution"><img src="https://agentmods.dev/badge/skills/chen3feng/agent-skills/test-layout-evolution.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What 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 5.1 | $0.00035 | $0.01612 |
| Opus 5.5 | $0.00014 | $0.00645 |
| Sonnet 5.5 | $0.00007 | $0.00322 |
| Haiku 4.5 | $0.00003 | $0.00161 |
Grade A, and why
test-layout-evolution 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 1mo ago.
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.
How it starts
The opening of the file, as written. The whole thing — 154 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Test layout evolution: unit tests vs. legacy test/
When to use
You are about to add the first real unit tests to a repository
that already has a directory called test/ (or tests/), but on
inspection that directory is not unit tests — it drives the
real binary end-to-end against fixture projects, boots a server,
shells out, or otherwise takes seconds per case.
Signal phrases: "there's already a test/ folder, I'll add mine
in there", "let's just add a test_xxx.py next to the existing
integration script", or a PR diff where a 10-ms mocked test
suddenly depends on testdata/, PATH, or network.
Problem
Conflating the two kinds of tests causes recurring pain:
- Speed and feedback loop. Integration suites are slow (real subprocess, real filesystem, real network) and can't run on every save. Unit suites are ~10ms and should run on every save. Put them in one directory and CI either pays the integration cost every time or never runs the units.
- Import / discovery conflicts. The legacy
test/is often not structured as a Python package at all (it's shell scripts- a driver). Dropping
test_*.pynext torun_tests.shconfuses pytest's collection and custom runners.
- a driver). Dropping
- Fixtures mismatch. Integration fixtures tend to live in
testdata/with real files; unit tests prefer in-memory mocks. Mixing them invites a unit test to accidentally open a fixture file and become a slow integration test with a unit test's name. - Dependency creep. Unit tests mock
run_command, network, clocks. Integration tests need those for real. Oneconftest.pytrying to serve both grows monkey-patches that silently break the integration side. - "Just refactor the old tests" is a trap. The integration suite is usually load-bearing for release gating and has accumulated non-obvious dependencies (env vars, working-dir assumptions, testdata). Moving it is a multi-PR project that should not block shipping the first unit test.
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.
- 1mo ago First seen · 154 lines · 35 tokens per session scan A 210c896345a3
test-layout-evolution is a skill published in the GitHub repository chen3feng/agent-skills (5 stars, last pushed 5mo ago), licensed Apache-2.0. It adds 35 tokens to every session and 1,612 once invoked, about $0.0001 per session on Opus 5.5. 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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