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 patrick-fu/awesome-skills --skill tddgit clone --depth 1 https://github.com/patrick-fu/awesome-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/patrick-fu/awesome-skills/tdd)<a href="https://agentmods.dev/skills/patrick-fu/awesome-skills/tdd"><img src="https://agentmods.dev/badge/skills/patrick-fu/awesome-skills/tdd/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/patrick-fu/awesome-skills/tdd"><img src="https://agentmods.dev/badge/skills/patrick-fu/awesome-skills/tdd.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 | $0.00029 | $0.00516 |
| Opus 5.5 | $0.00012 | $0.00206 |
| Sonnet 5.5 | $0.00006 | $0.00103 |
| Haiku 4.5 | $0.00003 | $0.00052 |
Grade A, and why
tdd 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 15d 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 — 61 lines — stays where its author put it; the contents beside it link to each section on GitHub.
TDD
Protect meaningful behavior with the smallest useful test set. Match the request: ordinary testing, regression work, or a requested test-first loop. A tests-only request keeps production changes outside its scope.
Contract
Read the relevant public surface, callers, existing tests and repository conventions. Identify the caller-visible contract, important failure risk and cheapest boundary that exercises it. Reuse accepted decisions; resolve only real contract ambiguity. Keep production APIs product-driven.
Minimum
Reuse checks that already protect the change. Add tests for distinct uncovered risks, not edited lines. Behavior-preserving refactors may need only existing checks. Prefer one readable test for one outcome, with the relevant assertions; split when independent behaviors or setups would obscure failures. Minimize redundancy without deleting distinct protection.
Mode
- Tests: exercise the subject with concrete inputs and independent expected outcomes. Choose the smallest realistic setup and true external boundary.
- TDD / regression: read Test-first for the red → green loop, failing-before evidence and after-fix sensitivity checks.
- Quality: also read Test quality before writing async tests or boundary doubles, and when pruning tests or evaluating suspect assertions, constants or overlapping coverage.
Proof
A useful test distinguishes a relevant defect while accepting equivalent implementations. Observe returned values, public state, persistence, events or boundary interactions when those interactions are the contract. Use real mechanisms or small faithful fakes where their behavior matters.
Tautological tests considered harmful. A result compared with itself has no independent oracle; obtain expectations from the contract or a worked example. Copying an algorithm can share its bug but is not necessarily a strictly tautological assertion.
Internal constant, prompt-string or source-shape pins usually protect no behavior; exercise the mechanism instead. Independently specified public values and absence of forbidden effects can be real contracts.
What ships with it
3 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.
- 15d ago First seen · 61 lines · 29 tokens per session scan A fbcda0eab171
tdd is a skill published in the GitHub repository patrick-fu/awesome-skills (69 stars, last pushed 4d ago), licensed MIT. It adds 29 tokens to every session and 516 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 2026-10-11.
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principle-test-behavior-not-implementation
Apply when you write, change, or keep a test. Assert what the code's users can observe, so that the test fails when that behavior breaks and keeps passing when only the internals change.
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This skill should be used when the user wants to implement features or fix bugs using test-driven development. Enforces the RED-GREEN-REFACTOR cycle with vertical slicing, context isolation between test writing and implementation, human checkpoints, and auto-test feedback loops. Uses multi-agent orchestration with the…
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mobiai-mobile-tdd
You MUST use this before writing any implementation code for a mobile feature, bug fix, refactor, or behavior change. Tests come before implementation — no exceptions.