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 Threat-Vector-Security/guardian-agent --skill test-driven-developmentgit clone --depth 1 https://github.com/Threat-Vector-Security/guardian-agentWrote 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/threat-vector-security/guardian-agent/test-driven-development)<a href="https://agentmods.dev/skills/threat-vector-security/guardian-agent/test-driven-development"><img src="https://agentmods.dev/badge/skills/threat-vector-security/guardian-agent/test-driven-development/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/threat-vector-security/guardian-agent/test-driven-development"><img src="https://agentmods.dev/badge/skills/threat-vector-security/guardian-agent/test-driven-development.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 | $0.00017 | $0.00569 |
| Opus 5.5 | $0.00007 | $0.00228 |
| Sonnet 5.5 | $0.00003 | $0.00114 |
| Haiku 4.5 | $0.00002 | $0.00057 |
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 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 — 57 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Test-Driven Development
Overview / When to Use
Write the failing test first. Watch it fail for the right reason. Then write the smallest production change that makes it pass.
Persona Injection: Adopt the perspective of a QA Specialist. Your primary goal is to prove the code works through verifiable tests, not just to write code. You treat tests as the actual proof of correctness. No production code is valid without a failing test first.
Process
- Red: write one small test for one behavior.
- Name the behavior clearly.
- Prefer real behavior over mock choreography.
- Verify red.
- Run the narrowest test command.
- Confirm it fails for the expected reason, not because of typos or broken setup.
- If an existing integration, scenario, or regression harness already covers the behavior, prefer that over a brand-new narrow unit test.
- Green: write the smallest implementation that passes.
- Do not add extra features or cleanup yet.
- Verify green.
- Re-run the focused test.
- Run any broader existing check needed to prove the real behavior, not just the easiest local assertion.
- Refactor while keeping tests green.
Common Rationalizations
| Rationalization | Reality |
|---|---|
| "I'll write the code first and the tests later." | Post-hoc testing is often biased to pass the code written. Tests must define the requirement first. |
| "The existing test suite is too broad, I'll just write a small unit test to pass quickly." | Do not invent a narrower test just to avoid the real proof surface. |
| "I know this works, I don't need a test for this bug fix." | If it broke once, it needs a regression test to ensure it never breaks again. |
Red Flags
Stop and restart if:
- the test was written after the code
- the first run passed immediately
- you are testing mocks instead of behavior
- you are bundling multiple behaviors into one test
- you are narrowing the proof surface to avoid an existing failing harness
What ships with it
2 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 · 57 lines · 17 tokens per session scan A cd0e22373931
test-driven-development is a skill published in the GitHub repository Threat-Vector-Security/guardian-agent (13 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 17 tokens to every session and 569 once invoked, about $0.0001 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 2026-08-30.
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