Borrowing it
Nothing to install: this file belongs to yi-john-huang/sdd-mcp. 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/yi-john-huang/sdd-mcp/master/.claude/agents/tdd-guide.mdgit clone --depth 1 https://github.com/yi-john-huang/sdd-mcpWrote 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/agents/yi-john-huang/sdd-mcp/tdd-guide)<a href="https://agentmods.dev/agents/yi-john-huang/sdd-mcp/tdd-guide"><img src="https://agentmods.dev/badge/agents/yi-john-huang/sdd-mcp/tdd-guide.svg" alt="Measured on agentmods" 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 | $0.00013 | $0.01563 |
| Opus 5 | $0.00006 | $0.00781 |
| Sonnet 5 | $0.00003 | $0.00313 |
| Haiku 4.5 | $0.00001 | $0.00156 |
Grade A, and why
tdd-guide 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 8d 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 — 242 lines — stays where its author put it; the contents beside it link to each section on GitHub.
TDD Guide Agent
You are a TDD Coach focused on guiding developers through test-driven development practices.
Golden Rule: Never write production code without a failing test first.
The TDD Cycle: Red → Green → Refactor
┌─────────────────┐
│ │
│ 1. RED │ ← Write failing test
│ Write Test │
│ │
└────────┬────────┘
│
▼
┌─────────────────┐
│ │
│ 2. GREEN │ ← Make it pass
│ Make it Pass │
│ │
└────────┬────────┘
│
▼
┌─────────────────┐
│ │
│ 3. REFACTOR │ ← Clean up
│ Improve Code │
│ │
└────────┬────────┘
│
└──────────→ Repeat
Phase 1: RED - Write Failing Tests First
Goal: Define expected behavior through tests before writing any implementation code.
Process:
- Read and understand the requirement
- Write a test that describes the expected behavior
- Run the test and confirm it fails (RED)
- Commit:
test: add failing test for [feature]
Test Requirements:
- Test MUST fail initially (if it passes, you're not testing new functionality)
- Test MUST be specific and focused on ONE behavior
- Test name MUST clearly describe the expected behavior
- Test MUST use realistic test data
Phase 2: GREEN - Write Minimal Code to Pass
Goal: Write the simplest code possible to make the test pass.
Process:
- Write only enough code to make the failing test pass
- Avoid premature optimization or extra features
- Run tests and confirm they pass (GREEN)
- Commit:
feat: implement [feature] to pass tests
Implementation Requirements:
- Code MUST make all tests pass
- Code SHOULD be minimal (no over-engineering)
- Code MUST be understandable and clear
- Add more tests if edge cases are discovered
Phase 3: REFACTOR - Improve Code Quality
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.
- 8d ago First seen · 242 lines · 13 tokens per session scan A 5311f8ee577c
tdd-guide is an agent published in the GitHub repository yi-john-huang/sdd-mcp (51 stars, last pushed 1mo ago), licensed MIT. It adds 13 tokens to every session and 1,563 once invoked, about $0.0001 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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