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/matrixfounder/agentic-development/tdd-stub-firstnpx skills add MatrixFounder/Agentic-development --skill tdd-stub-firstgit clone --depth 1 https://github.com/MatrixFounder/Agentic-developmentWrote 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/matrixfounder/agentic-development/tdd-stub-first)<a href="https://agentmods.dev/skills/matrixfounder/agentic-development/tdd-stub-first"><img src="https://agentmods.dev/badge/skills/matrixfounder/agentic-development/tdd-stub-first.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 | $0.00016 | $0.00264 |
| Opus 5 | $0.00008 | $0.00132 |
| Sonnet 5 | $0.00003 | $0.00053 |
| Haiku 4.5 | $0.00002 | $0.00026 |
Grade A, and why
tdd-stub-first 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 4d 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 & Stub-First Strategy
1. Stubbing Phase
- Create Structure: Files, classes, methods.
- Implement Stubs: Use
NotImplementedError,return None, or hardcoded values. - Docstrings: Add detailed docstrings describing future logic.
- E2E Test (Stub): Write an E2E test that asserts the hardcoded behavior.
- Example: asserting
discount == 100.0(stubbed value).
- Example: asserting
2. Implementation Phase
- Verify Stubs: Ensure E2E test passes on stubs.
- Replace Stubs: Implement real logic.
- Unit Tests: Add unit tests for specific methods and edge cases.
- Update E2E: Update E2E test to assert real behavior.
- Example: asserting
discount == 150.0(calculated value).
- Example: asserting
3. Testing Rules
- No Mocking LLMs: Use recorded responses or separate integration environments.
- Regression: Always run full regression suite.
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.
- 4d ago First seen · 26 lines · 16 tokens per session scan A 7ecc015e27db
tdd-stub-first is a skill published in the GitHub repository MatrixFounder/Agentic-development (5 stars, last pushed yesterday), licensed Apache-2.0. It adds 16 tokens to every session and 264 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 2026-08-31.
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