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 tjboudreaux/cc-plugin-engineering-excellence --skill eng-tddgit clone --depth 1 https://github.com/tjboudreaux/cc-plugin-engineering-excellenceWrote 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/tjboudreaux/cc-plugin-engineering-excellence/eng-tdd)<a href="https://agentmods.dev/skills/tjboudreaux/cc-plugin-engineering-excellence/eng-tdd"><img src="https://agentmods.dev/badge/skills/tjboudreaux/cc-plugin-engineering-excellence/eng-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/tjboudreaux/cc-plugin-engineering-excellence/eng-tdd"><img src="https://agentmods.dev/badge/skills/tjboudreaux/cc-plugin-engineering-excellence/eng-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 | $0.00035 | $0.00639 |
| Opus 5 | $0.00017 | $0.00319 |
| Sonnet 5 | $0.00007 | $0.00128 |
| Haiku 4.5 | $0.00003 | $0.00064 |
Grade A, and why
eng-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 9d 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 — 70 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Test-Driven Development (TDD)
Overview
Write the test first. Watch it fail. Implement just enough to pass. Refactor while staying green. If you didn’t see the test fail, you don’t know whether it tests the right behavior.
Iron Law
NO PRODUCTION CODE WITHOUT A FAILING TEST FIRST
Wrote code before the test? Delete it. Start from tests.
When to Use
- Every feature, bug fix, refactor, or behavior change.
- Exceptions only with explicit human approval (throwaway prototypes, generated code, etc.).
Red-Green-Refactor Cycle
- RED – Write one minimal test describing desired behavior.
- Clear, specific name.
- Tests real behavior (avoid unnecessary mocks).
- Verify RED – Run the test; confirm it fails for the expected reason.
- GREEN – Write the simplest code to make the test pass. No extra features.
- Verify GREEN – Run the test suite; ensure the new test and existing tests pass.
- REFACTOR – Clean up code/tests while keeping everything green.
- Repeat for next behavior.
Good vs Bad Tests
| Good | Bad |
|---|---|
| Tests one thing | Vague “does work” |
| Clear name | test1 |
| Real behavior | Asserts on mocks |
Why Order Matters
- Tests written after code pass immediately → prove nothing.
- Manual testing isn’t reproducible evidence.
- Keeping prewritten code “for reference” breaks TDD—delete and rebuild from tests.
Rationalization Countermeasures
| Excuse | Response |
|---|---|
| “Too simple” | Simple code breaks—test anyway. |
| “I’ll test later” | Tests-after confirm existing behavior, not requirements. |
| “Manual testing is enough” | No record or rerun; automation is required. |
| “Deleting work is wasteful” | Sunk cost; untested code is debt. |
| “Being pragmatic” | TDD prevents debugging hell; pragmatism = reliability. |
Verification Checklist
- Every new behavior guarded by a test.
- Saw each test fail before implementation.
- Each failure was due to missing behavior (not typos).
- Wrote minimal code to make each test pass.
- Full suite green after changes.
- Refactors done only while green.
- Tests cover edge/error cases.
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.
- 9d ago First seen · 70 lines · 35 tokens per session scan A 8310d7fe2df4
eng-tdd is a skill published in the GitHub repository tjboudreaux/cc-plugin-engineering-excellence (4 stars, last pushed 7mo ago), licensed MIT. It adds 35 tokens to every session and 639 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 2026-08-31.
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