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/ahonn/dotfiles/tddnpx skills add ahonn/dotfiles --skill tddgit clone --depth 1 https://github.com/ahonn/dotfilesWrote 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/ahonn/dotfiles/tdd)<a href="https://agentmods.dev/skills/ahonn/dotfiles/tdd"><img src="https://agentmods.dev/badge/skills/ahonn/dotfiles/tdd.svg" alt="Measured on agentmods" 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 | $0.00119 | $0.00977 |
| Opus 5 | $0.00060 | $0.00489 |
| Sonnet 5 | $0.00024 | $0.00195 |
| Haiku 4.5 | $0.00012 | $0.00098 |
Grade A, and why
tdd 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.
How it starts
The opening of the file, as written. The whole thing — 49 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Test-Driven Development
TDD is the red → green loop. This skill is the reference that makes that loop produce tests worth keeping: what a good test is, where tests go, the anti-patterns, and the rules of the loop. Every section applies on every cycle — consult them before and during the loop, not after.
Not the default workflow. Most tasks use AGENTS.md test modes skip, verify-only, or add-tests without this skill. Only continue past the gate when mode is tdd (or the user explicitly ordered test-first).
When exploring the codebase, read the project's domain docs if they exist (CLAUDE.md, glossary, ADRs) so test names and interface vocabulary match the project's domain language.
Gate (before any red test)
Answer all three before writing a failing test:
- Harness? Is there a runnable test runner for this change surface (or is the user asking to introduce one for real domain logic)?
- Logic-bearing? Is the behavior domain logic / regression-worthy — not config, docs, Nix, pure UI chrome, rename, or scaffolding?
- Opt-in? Did the user ask for TDD/test-first/red-green, or is AGENTS test mode explicitly
tdd?
If any answer is no → stop. State Test mode: skip | verify-only | add-tests and a one-line rationale. Do not invent a harness, force red→green, or load the rest of this skill as a mandatory process.
What a good test is
Tests verify behavior through public interfaces, not implementation details. Code can change entirely; tests shouldn't. A good test reads like a specification — "user can checkout with valid cart" tells you exactly what capability exists — and survives refactors because it doesn't care about internal structure.
See tests.md for examples and mocking.md for mocking guidelines.
Seams — where tests go
A seam is the public boundary you test at: the interface where you observe behavior without reaching inside. Tests live at seams, never against internals.
Test only at pre-agreed seams. Before writing any test, write down the seams under test and confirm them with the user. No test is written at an unconfirmed seam. You can't test everything — agreeing the seams up front is how testing effort lands on the critical paths and complex logic instead of every edge case.
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 · 119 tokens per session scan A fae7ff3f767c
tdd is a skill published in the GitHub repository ahonn/dotfiles (62 stars, last pushed 4d ago), licensed MIT. It adds 119 tokens to every session and 977 once invoked, about $0.0006 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 2026-09-03.
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