Borrowing it
Nothing to install: this file belongs to thedaviddias/skill-check. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/thedaviddias/skill-check/main/.agents/skills/tdd-methodoly-expert/SKILL.mdgit clone --depth 1 https://github.com/thedaviddias/skill-checkWrote 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/thedaviddias/skill-check/tdd-methodoly-expert)<a href="https://agentmods.dev/skills/thedaviddias/skill-check/tdd-methodoly-expert"><img src="https://agentmods.dev/badge/skills/thedaviddias/skill-check/tdd-methodoly-expert/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/thedaviddias/skill-check/tdd-methodoly-expert"><img src="https://agentmods.dev/badge/skills/thedaviddias/skill-check/tdd-methodoly-expert.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 | $0.00053 | $0.01990 |
| Opus 5 | $0.00026 | $0.00995 |
| Sonnet 5 | $0.00011 | $0.00398 |
| Haiku 4.5 | $0.00005 | $0.00199 |
Grade A, and why
tdd-methodoly-expert 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 — 288 lines — stays where its author put it; the contents beside it link to each section on GitHub.
TDD Methodology Expert
Enforce and reinforce Test-Driven Development (TDD) methodology throughout the software development process. This skill provides comprehensive guidance, automated validation, and continuous reinforcement of the Red-Green-Refactor cycle.
When to Use This Skill
This skill automatically activates when:
- TDD is mentioned in
CLAUDE.mdorCLAUDE.local.md - TDD is referenced in project memory
- The user explicitly requests TDD methodology
- The user asks to write tests or implement features
Use this skill for:
- Implementing new features using TDD
- Refactoring existing code with test protection
- Fixing bugs with test-first approach
- Ensuring code quality through TDD discipline
- Validating that TDD principles are being followed
Do NOT use this skill for:
- Pure design discussions without implementation
- Documentation-only tasks
- Research or exploration tasks
Core TDD Methodology
Test-Driven Development follows a strict three-phase cycle that must be repeated for every increment of functionality:
🔴 Red Phase: Write a Failing Test
Always write the test before any production code.
- Write a test that expresses the desired behavior
- Run the test and verify it fails (for the right reason)
- Confirm the failure message indicates what's missing
Red Phase Principles:
- Test must be simple and focused on one behavior
- Test name should clearly describe expected behavior
- Test should be readable without looking at implementation
- Failure should be meaningful and guide implementation
Example Flow:
1. Write: test_should_calculate_total_with_tax()
2. Run: Test fails - "ShoppingCart has no attribute 'calculate_total'"
3. ✅ Ready for Green phase
🟢 Green Phase: Make the Test Pass
Write minimal code to make the failing test pass.
- Implement the simplest code that makes the test pass
- Run the test and verify it passes
- Run all tests to ensure nothing broke
Green Phase Principles:
- Write only enough code to pass the current test
- Don't add features not required by tests
- It's okay to use shortcuts (you'll refactor later)
- Focus on making it work, not making it perfect
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.
- 9d ago First seen · 288 lines · 53 tokens per session scan A 1b59d1ad3be1
tdd-methodoly-expert is a skill published in the GitHub repository thedaviddias/skill-check (188 stars, last pushed 3mo ago), licensed MIT. It adds 53 tokens to every session and 1,990 once invoked, about $0.0003 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.
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