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 ashermahonin/agentic-skills --skill tdd-workflowgit clone --depth 1 https://github.com/ashermahonin/agentic-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/ashermahonin/agentic-skills/tdd-workflow)<a href="https://agentmods.dev/skills/ashermahonin/agentic-skills/tdd-workflow"><img src="https://agentmods.dev/badge/skills/ashermahonin/agentic-skills/tdd-workflow.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 5.1 | $0.00066 | $0.00641 |
| Opus 5 | $0.00033 | $0.00320 |
| Sonnet 5 | $0.00013 | $0.00128 |
| Haiku 4.5 | $0.00007 | $0.00064 |
Grade A, and why
tdd-workflow 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 8d 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 — 61 lines — stays where its author put it; the contents beside it link to each section on GitHub.
TDD Workflow
Purpose
Turn an acceptance criterion into executable evidence before production code changes. This skill owns the test contract and proof; service-implementation owns production edits.
When a route also includes service-implementation, this skill owns the test contract, red evidence, anti-overfit criteria, and reproduction commands. service-implementation owns the production code change under that contract. When this skill is used alone, it may execute the full red/green/refactor loop itself.
Change context
- Read
references/tdd-loop.md. - State the changed behavior and the acceptance criterion it satisfies.
- Choose the lowest test level that can prove the behavior without mocking away the risk.
- Confirm the repository's test command and current framework behavior before writing the test.
Change method
- Write one test for one observable behavior and run it before changing production code.
- Confirm that it fails because the behavior is missing or wrong, not because the test setup is broken.
- Hand
service-implementationthe expected behavior, owned files, prohibited shortcuts, and exact verification command. - After implementation, run the new test and the affected suite. Do not weaken assertions to obtain a pass.
- Add one meaningful boundary, invalid-input, or failure-path case that the first test did not cover.
- Refactor only while the affected suite remains green; use
engineering-qualitywhen structure or maintainability is part of the change. - Map each covered acceptance criterion to a test file and list anything still unproved.
Engineering constraints
- Use current test-runner documentation when syntax, fixtures, matchers, or isolation behavior is uncertain.
- Record what the chosen test level proves and what it cannot prove.
- Do not require test-first work when no automated test can provide useful evidence; document the alternative verification path instead.
- Never delete, skip, or weaken an existing test solely to make a change pass.
What ships with it
2 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.
- 8d ago First seen · 61 lines · 66 tokens per session scan A 201cb83dfa69
tdd-workflow is a skill published in the GitHub repository ashermahonin/agentic-skills (10 stars, last pushed 14d ago), licensed MIT. It adds 66 tokens to every session and 641 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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