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 agentmods add skills/tx1207/hello-scholar/test-driven-developmentnpx skills add Tx1207/hello-scholar --skill test-driven-developmentgit clone --depth 1 https://github.com/Tx1207/hello-scholarWhat 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 | $0.00037 | $0.03076 |
| Opus 5 | $0.00018 | $0.01538 |
| Sonnet 5 | $0.00007 | $0.00615 |
| Haiku 4.5 | $0.00004 | $0.00308 |
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 2d 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 — 399 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Test-Driven Development (TDD)
Explicit Entry Gate
Enter this skill only when one of these facts is present:
- The user explicitly requests
$test-driven-development,TDD,test-first, orRed-Green-Refactor. - The current Approved Task explicitly requires a
TDD Processor explicitly namesTDD,test-first, orRed-Green-Refactoras its process.
A request to add tests, or Validation: npm test, is ordinary implementation and validation; it does not enter this skill by itself. Do not infer TDD from task type, testing language, or validation commands.
If neither fact is present, exit this skill immediately. Follow the applicable AGENTS/Task instructions for ordinary implementation and validation; do not impose this TDD workflow or redo existing code.
After entry, follow the full process below. Tests after are not TDD. If a user who explicitly requested TDD later calls the work a throwaway prototype, generated code, or configuration file, ask whether they are revoking the TDD request; do not choose that exception yourself.
Overview
Write the test first. Watch it fail. Write minimal code to pass.
Core principle: If you didn't watch the test fail, you don't know if it tests the right thing.
Confirm the Seam
Before RED, name the public interface or observable behavior that this slice will test—the seam. Reuse a seam explicitly named in the user request or Approved Task; otherwise ask one bounded question: "What public interface or observable behavior should this slice verify?" Do not write evidence against an unconfirmed internal collaborator or private method.
Completion criterion: The current slice has one confirmed seam and one observable behavior.
Violating the letter of the rules is violating the spirit of the rules.
Evidence Artifacts
In this skill, a "test" means the cheapest evidence artifact that can fail for the right reason before implementation. For ordinary deterministic code, that is usually a unit or integration test. For AI, agent, RAG, prompt, skill, or research work, it may be an eval case, trajectory check, benchmark smoke run, scorer, or pressure scenario.
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.
- 2d ago First seen · 399 lines · 37 tokens per session scan A 252007b82bfd
test-driven-development is a skill published in the GitHub repository Tx1207/hello-scholar (5 stars, last pushed 21d ago), licensed MIT. It adds 37 tokens to every session and 3,076 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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