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 jcwleo/oh-no-harness --skill test-driven-developmentgit clone --depth 1 https://github.com/jcwleo/oh-no-harnessWrote 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/jcwleo/oh-no-harness/test-driven-development)<a href="https://agentmods.dev/skills/jcwleo/oh-no-harness/test-driven-development"><img src="https://agentmods.dev/badge/skills/jcwleo/oh-no-harness/test-driven-development.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 | $0.00042 | $0.02721 |
| Opus 5 | $0.00021 | $0.01360 |
| Sonnet 5 | $0.00008 | $0.00544 |
| Haiku 4.5 | $0.00004 | $0.00272 |
Grade A, and why
test-driven-development 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 6d 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 — 289 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Test Driven Development for Claude Code
This generated file is the Claude Code-facing runtime skill document. Claude Code slash commands should read this file directly; maintainers edit the source documents listed below instead.
Generated Runtime Composition
Source order:
../../docs/skill-core/test-driven-development.md../../docs/platforms/claude-code-runtime.md
The sections below are already composed for this platform. Do not ask the runtime model to load another platform's runtime document or invocation syntax.
Source: docs/skill-core/test-driven-development.md
Test Driven Development
Write the test first. Watch it fail. Write the smallest production change that makes it pass. Refactor only after green.
Software Development Stage
Test Driven Development is the internal mid-loop discipline for behavior-change work inside implementation and bug-fix execution.
Use it inside ralph, systematic-debugging, or ultrawork before changing production behavior. It is not a requirements, planning, cleanup, or final-verification substitute.
Top-Level Routing Boundary
Do not use this skill as the top-level route for ordinary implementation
requests such as "add this feature", "fix this bug", "refactor this module",
or "implement this behavior". This is not a top-level implementation skill.
Use ralph for those concrete implementation requests so execution mode,
worktree isolation, review, cleanup, verification, and final reporting stay
attached to the work.
Use this skill as a top-level entry only when:
- the user explicitly asked for TDD, test-first, RED/GREEN/REFACTOR, or "write the failing test first"
- an already-selected workflow (
ralph,systematic-debugging, orultrawork) reaches its internal TDD gate
Direct-edit-eligible mutations are inert and never reach this skill;
other small concrete edits route through ralph, which may apply its STANDARD
small-task carve-out; there is no
separate direct edit path that reaches this skill outside a workflow or an
explicit user TDD request.
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.
- 6d ago First seen · 289 lines · 42 tokens per session scan A 04b8f91a3d27
test-driven-development is a skill published in the GitHub repository jcwleo/oh-no-harness (11 stars, last pushed 29d ago), licensed MIT. It adds 42 tokens to every session and 2,721 once invoked, about $0.0002 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 2026-08-30.
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strict-tdd
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tdd
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You MUST use this before writing any implementation code for a mobile feature, bug fix, refactor, or behavior change. Tests come before implementation — no exceptions.