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 xonovex/platform --skill tdd-guidegit clone --depth 1 https://github.com/xonovex/platformWrote 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/xonovex/platform/tdd-guide)<a href="https://agentmods.dev/skills/xonovex/platform/tdd-guide"><img src="https://agentmods.dev/badge/skills/xonovex/platform/tdd-guide/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/xonovex/platform/tdd-guide"><img src="https://agentmods.dev/badge/skills/xonovex/platform/tdd-guide.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 | $0.00135 | $0.00963 |
| Opus 5.5 | $0.00054 | $0.00385 |
| Sonnet 5.5 | $0.00027 | $0.00193 |
| Haiku 4.5 | $0.00014 | $0.00096 |
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 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.
How it starts
The opening of the file, as written. The whole thing — 50 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Test-Driven Development
Drive production code from a failing test, one small step at a time: red (write a test that fails), green (make it pass by any means), refactor (remove the duplication you just created). The goal is clean code that works, and the design emerges from the tests rather than being drawn up front.
Essentials
- Run the loop red -> green -> refactor - never skip refactor; green-without-refactor is not TDD, see references/red-green-refactor.md
- Write the failing test before the code - production code exists only to make a red test pass, see references/red-green-refactor.md
- Pick a green-bar strategy per step - obvious implementation, fake it, or triangulate, see references/green-bar-strategies.md
- Keep a test list, work one item at a time - list test ideas, never batch-write them, see references/test-list-and-design.md
- Let the tests grow the design - the emerging API is an output; judge the refactor against oop-guide and connascence-guide, see references/test-list-and-design.md
Gotchas
- Skipping refactor leaves the duplication you committed to go green (including a constant duplicated between test and code): removing it is exactly what the third step is for.
- "Refactor" means change structure without changing behaviour while the test stays green; it is not "rewrite", "optimize", or "add the next feature".
- The test list is a list of test IDEAS, not a batch of tests written up front: write them one at a time to preserve the cycle.
- Test-first is the rhythm; classical vs mockist is an orthogonal design choice. You can do classical TDD test-first, so don't conflate the two.
- Neither classical nor mockist is "more modern": mockist trades integration coverage and tighter implementation-coupling for faster, smaller fixtures.
- A single good test's anatomy (AAA, FIRST, naming, the test-double taxonomy) belongs to testing-guide. This skill owns only the rhythm in which you write it.
What ships with it
7 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.
- 1mo ago First seen · 50 lines · 135 tokens per session scan A dcea979a957f
tdd-guide is a skill published in the GitHub repository xonovex/platform (6 stars, last pushed 4d ago), licensed MIT. It adds 135 tokens to every session and 963 once invoked, about $0.0005 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 2026-09-08.
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