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 YSAA1/harness-workflow --skill tddgit clone --depth 1 https://github.com/YSAA1/harness-workflowWrote 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/ysaa1/harness-workflow/tdd)<a href="https://agentmods.dev/skills/ysaa1/harness-workflow/tdd"><img src="https://agentmods.dev/badge/skills/ysaa1/harness-workflow/tdd/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/ysaa1/harness-workflow/tdd"><img src="https://agentmods.dev/badge/skills/ysaa1/harness-workflow/tdd.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 | $0.00046 | $0.00533 |
| Opus 5.5 | $0.00018 | $0.00213 |
| Sonnet 5.5 | $0.00009 | $0.00107 |
| Haiku 4.5 | $0.00005 | $0.00053 |
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 7d 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 — 31 lines — stays where its author put it; the contents beside it link to each section on GitHub.
TDD (red → green)
Tests verify behavior on public interfaces, not implementation details; the implementation can be replaced wholesale without the tests having to follow. Consult this file before each loop starts, not after the fact.
Seams: where tests go
A seam is a public boundary for observing behavior: an interface where behavior changes are visible without digging into internals. Tests live only on seams and are never written against internals.
Test only on pre-agreed seams. Before writing any test, write down the seams to be tested and confirm them with the user, or adopt the acceptance surface of an approved Spec/plan; write no tests on unconfirmed seams. How to ask: "What is the public interface? Which seams are worth testing?" Give each proposed seam a one-line note on what it catches and what it misses.
A good test reads like a specification ("user can checkout with valid cart") and survives refactoring. Good/bad contrasts are in references/tests.md; mock boundaries are in references/mocking.md.
Loop rules
- Red first, green second. Write the failing test first, then just enough implementation to make it pass; do not pre-write future tests or add speculative features.
- One slice at a time. Each loop covers one seam, one test, one minimal piece of implementation; a vertical slice rather than laying things out horizontally — writing all the tests first and then all the implementations verifies only imagined behavior.
- Refactoring is not part of the loop. Structural convergence after the behavior is green is identified by review and tidied up separately once authorized; it is not mixed into the red-green loop.
Anti-patterns
- Implementation coupling: mocking internal collaborators, testing private methods, verifying through a side door. Detection signal: the behavior did not change, yet the test went red after refactoring.
- Tautology: the assertion recomputes the expected value the same way the implementation does, passing by construction. Expected values must come from an independent source of truth: known-correct literals, precomputed examples, or the Spec.
- Horizontal slicing: see "One slice at a time".
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.
- 7d ago Changed b898f1d4d40b
- 23d ago Changed ceda777cf3d3
- 1mo ago First seen · 31 lines · 46 tokens per session scan A 21114d2b3a72
tdd is a skill published in the GitHub repository YSAA1/harness-workflow (3 stars, last pushed 8d ago), licensed MIT. It adds 46 tokens to every session and 533 once invoked, about $0.0002 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 2026-09-16.
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