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 perniemann/pnCore --skill pn-tddgit clone --depth 1 https://github.com/perniemann/pnCoreWrote 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/perniemann/pncore/pn-tdd)<a href="https://agentmods.dev/skills/perniemann/pncore/pn-tdd"><img src="https://agentmods.dev/badge/skills/perniemann/pncore/pn-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/perniemann/pncore/pn-tdd"><img src="https://agentmods.dev/badge/skills/perniemann/pncore/pn-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 | $0.00036 | $0.00315 |
| Opus 5.5 | $0.00014 | $0.00126 |
| Sonnet 5.5 | $0.00007 | $0.00063 |
| Haiku 4.5 | $0.00004 | $0.00032 |
Grade A, and why
pn-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 1mo 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.
What it actually says
TDD (Test-Driven Development)
When to use
- Implementing a new feature or bug fix with test-first discipline (RED-GREEN-REFACTOR).
- Production code was written before a failing test and needs to be reset to follow TDD correctly.
- You want to enforce one-behavior-at-a-time discipline and prevent speculative code.
Iron rule
Do not write production code before a failing test. If production code was written before a failing test, delete that production code and restart with a failing test first.
Workflow (RED-GREEN-REFACTOR)
- RED: Write the smallest failing test that defines the desired behavior. Run it; it must fail.
- GREEN: Write the minimal production code to make the test pass. No extra behavior.
- REFACTOR: Improve the code (naming, duplication, structure) while keeping tests green.
- Repeat for the next behavior.
Guardrails
- One behavior at a time; small test, minimal code.
- Run tests after every change.
- If you wrote production code first, remove it and write the failing test first.
Output
- Failing test (RED), then passing (GREEN), then refactor summary.
- Clear link between each test and the production code that satisfies it.
What ships with it
1 file 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.
- 1mo ago First seen · 35 lines · 36 tokens per session scan A e730df6058bd
pn-tdd is a skill published in the GitHub repository perniemann/pnCore (0 stars, last pushed 2d ago), licensed MIT. It adds 36 tokens to every session and 315 once invoked, about $0.0001 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 2026-09-03.
Other skills, from other repositories
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Find the root cause, implement a focused fix, and prove behavior with targeted tests and recordings.
taiyi-dev
A software-development stage that implements planned tasks using test-driven development, or TDD: write a failing test, make it pass, then improve the code. It checks the task plan, dependencies, file boundaries, and required completion evidence.
maestro-work
The contract every playbook shares - the brief a writer receives, the rules it writes by, the handback it returns, and the store record the holder keeps. Reuse existing checks and add tests only for concrete uncovered behavior or risk.
contract
Outcome-driven Cortex function development — declares a behavioral contract before generation begins, enforces evidence-tiered proof before $ship, and defends against the self-oracle evaluation failure mode.
test-driven-development
Writing code with tests first: RED-GREEN-REFACTOR, reproduce bugs as failing tests before fixing, and avoid testing anti-patterns. Use when implementing behaviour, fixing a defect, or asked to add tests.
test-driven-development
Rigorous TDD methodology enforcing RED-GREEN-REFACTOR discipline. Use when implementing features or fixing bugs during the implement phase. Tests must be written before production code - no exceptions.