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 helmedeiros/clean-code-skills --skill tdd-test-firstgit clone --depth 1 https://github.com/helmedeiros/clean-code-skillsWrote 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/helmedeiros/clean-code-skills/tdd-test-first)<a href="https://agentmods.dev/skills/helmedeiros/clean-code-skills/tdd-test-first"><img src="https://agentmods.dev/badge/skills/helmedeiros/clean-code-skills/tdd-test-first/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/helmedeiros/clean-code-skills/tdd-test-first"><img src="https://agentmods.dev/badge/skills/helmedeiros/clean-code-skills/tdd-test-first.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 | $0.00049 | $0.00712 |
| Opus 5 | $0.00024 | $0.00356 |
| Sonnet 5 | $0.00010 | $0.00142 |
| Haiku 4.5 | $0.00005 | $0.00071 |
Grade A, and why
tdd-test-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 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 — 67 lines — stays where its author put it; the contents beside it link to each section on GitHub.
TDD: Test-First Approach
Enforce the discipline of writing tests before production code to ensure that every behavior is specified, verified, and designed for testability from the start.
When This Skill Applies
- The user wants to add a new feature or fix a bug
- The user mentions writing tests first or test-first development
- Code is being written without corresponding tests
- The user wants to improve testability of existing code
Core Principle
Write the test before the code it tests. A test-first approach forces you to think about the desired behavior and public API before committing to an implementation. Code that is hard to test is usually hard to use — test-first design produces better interfaces naturally.
Workflow
Step 1: Define the Desired Behavior
State in plain language what the code should do. Focus on observable outcomes, not implementation details. Ask: "What should the caller see happen?"
Step 2: Write the Test
Translate the behavior into a test. Choose a descriptive name. Set up the minimum context (Arrange), invoke the behavior (Act), and verify the outcome (Assert). Do not write any production code yet.
Step 3: Watch It Fail
Run the test and confirm it fails for the right reason — typically a missing class, method, or incorrect return value. If it fails for an unexpected reason (syntax error, wrong import), fix the test first.
Step 4: Implement Just Enough
Write the simplest production code that makes the test pass. Do not anticipate future requirements.
Step 5: Verify and Continue
Run the full suite. If green, consider the next behavior. If a test breaks, fix the issue before moving on.
Detection / Indicators
- Production code exists without a corresponding test
- Tests were added after the code was "done"
- Tests mirror implementation structure instead of describing behavior
- The user writes a full class before any test
- Mocking is excessive because the code was not designed for testability
Transformation Pattern
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 · 67 lines · 49 tokens per session scan A 325b04798362
tdd-test-first is a skill published in the GitHub repository helmedeiros/clean-code-skills (2 stars, last pushed 6mo ago), licensed MIT. It adds 49 tokens to every session and 712 once invoked, about $0.0002 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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