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 vinnie357/claude-skills --skill tddgit clone --depth 1 https://github.com/vinnie357/claude-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/vinnie357/claude-skills/tdd)<a href="https://agentmods.dev/skills/vinnie357/claude-skills/tdd"><img src="https://agentmods.dev/badge/skills/vinnie357/claude-skills/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/vinnie357/claude-skills/tdd"><img src="https://agentmods.dev/badge/skills/vinnie357/claude-skills/tdd.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00043 | $0.03280 |
| Opus 5 | $0.00022 | $0.01640 |
| Sonnet 5 | $0.00009 | $0.00656 |
| Haiku 4.5 | $0.00004 | $0.00328 |
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 10d 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 — 334 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Test-Driven Development
A discipline for growing software guided by tests, one small step at a time.
The TDD Cycle
Five Steps
- Write a test list — brainstorm the tests you think you'll need
- Write one failing test — pick the next test from the list
- Make it pass — write the simplest code that makes the test green
- Refactor — remove duplication and improve design, keeping tests green
- Repeat — pick the next test, update the list as you learn
Red-Green-Refactor
The micro-cycle is a three-state machine:
┌──────────────────────────────────────┐
│ │
▼ │
[RED] ──── write minimal code ────► [GREEN] ──── refactor ────► [GREEN]
▲ │
│ │
└──────────── write next failing test ◄──────────────────────────┘
RED: Write a test that fails. Confirm it fails for the right reason — the missing behavior, not a syntax error or wrong import.
GREEN: Make the test pass with the simplest change possible. "Sinful" code is fine — hardcoded values, copy-paste, whatever gets green fastest.
REFACTOR: Clean up while all tests stay green. Remove duplication between test and production code. Improve names. Extract methods. This is where design emerges.
Rules:
- Never write production code without a failing test
- Never write more test code than needed to fail
- Never write more production code than needed to pass
The Three Laws
Uncle Bob's formalization of Beck's constraints:
- You shall not write production code unless you have a failing test
- You shall not write more of a test than is sufficient to fail (including compile failures)
- You shall not write more production code than is sufficient to pass the currently failing test
These laws enforce the micro-cycle. They keep steps small and feedback immediate.
What ships with it
4 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.
- 10d ago First seen · 334 lines · 43 tokens per session scan A e6656a8a8ebe
tdd is a skill published in the GitHub repository vinnie357/claude-skills (25 stars, last pushed today), licensed MIT. It adds 43 tokens to every session and 3,280 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.
Other skills, from other repositories
engram-testing-coverage
TDD and coverage standards for Engram. Trigger: When implementing behavior changes in any package.
iterative-development
TDD iteration loops using Claude Code Stop hooks - runs tests after each response, feeds failures back automatically.
python
Python development with ruff, mypy, pytest - TDD and type safety.
nw-fp-clojure
Clojure language-specific patterns, data-first modeling, REPL-driven development, and spec.
strict-tdd
Strict RED->GREEN->REFACTOR test-driven development with enforcement. Never write production code before a failing test. Atomic commits per TDD cycle.
mobiai-mobile-tdd
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.