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 bartoszarendt/agenticloop --skill tdd-implementationgit clone --depth 1 https://github.com/bartoszarendt/agenticloopWrote 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/bartoszarendt/agenticloop/tdd-implementation)<a href="https://agentmods.dev/skills/bartoszarendt/agenticloop/tdd-implementation"><img src="https://agentmods.dev/badge/skills/bartoszarendt/agenticloop/tdd-implementation/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/bartoszarendt/agenticloop/tdd-implementation"><img src="https://agentmods.dev/badge/skills/bartoszarendt/agenticloop/tdd-implementation.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 | $0.00064 | $0.00773 |
| Opus 5.5 | $0.00026 | $0.00309 |
| Sonnet 5.5 | $0.00013 | $0.00155 |
| Haiku 4.5 | $0.00006 | $0.00077 |
Grade A, and why
tdd-implementation 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 — 87 lines — stays where its author put it; the contents beside it link to each section on GitHub.
TDD implementation
No production code without a failing test or failing check first when behavior changes. A test written after the code passes immediately and proves little: it never demonstrated that it can catch the missing behavior.
The cycle
- RED: write one minimal test or check for the next required behavior from the task record.
- Verify RED: run it and confirm it fails for the expected reason.
- GREEN: write the smallest production change that passes.
- Verify GREEN: run the focused check, then the task's Required Checks.
- REFACTOR: clean names and duplication while everything is green.
Keep the RED output. The implementation summary needs it under [[verification-evidence]].
For bugfixes, RED is the reproduction of the bug. For review revisions, RED covers the gap identified by [[review-and-accept]].
If production code already exists before its test, temporarily disable or revert the behavior, watch the new test fail, then restore the behavior. Otherwise the test is unverified.
Test through a public seam
Use the highest useful public interface that exercises the behavior:
- service or repository method,
- API route,
- CLI command,
- rendered component,
- user-facing workflow.
Assert observable behavior, not private helper calls or internal fields. Prefer real collaborators over mocks where practical.
Vertical slices
Do not write a batch of imagined tests and then a batch of implementation. Run one behavior at a time:
RED -> GREEN -> REFACTOR
RED -> GREEN -> REFACTOR
Horizontal slicing hides which behavior is actually being built and encourages brittle tests.
Scaffold and infra tasks
Some tasks have no unit-testable behavior. The principle still applies through the Required Checks:
- config validation,
- lint/typecheck,
- smoke command,
- migration dry run,
- package/build command.
If a task is genuinely unverifiable, say so under Known Limitations. Do not write fake tests just to satisfy a checklist.
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 · 87 lines · 64 tokens per session scan A 6c362aae1e40
tdd-implementation is a skill published in the GitHub repository bartoszarendt/agenticloop (2 stars, last pushed 1mo ago), licensed MIT. It adds 64 tokens to every session and 773 once invoked, about $0.0003 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 2026-08-31.
Other skills, from other repositories
08-debug
Reproduce and fix a known bug, or find an unknown root cause by hypothesis validation. Use when the user wants to fix a bug, find why something breaks, or reopen a stuck investigation. Not for building a feature or reviewing a diff.
systematic-debugging
Structured root-cause debugging loop — reproduce, isolate, form a hypothesis, verify the fix. Use whenever a bug, crash, test failure, or unexpected behavior is reported.
test-driven-development
Test-driven development discipline — write a failing test, implement the minimum to pass, then refactor. Use when adding a feature or fixing a bug where correctness matters.
Test Driven Development
Drive behavior changes through a failing test, the smallest working implementation, and then cleanup once the behavior is locked.
foreman-tdd
Stack-agnostic test-driven development loop for a single Foreman issue. Implements one vertical slice with strict red-green-refactor (one test at a time, never horizontal slicing) using the foreman-test wrapper, saves completion evidence, then emits a machine-readable FOREMAN-SUMMARY block Foreman parses.
superpowers-test-driven-development
Use when implementing any feature or bugfix, before writing implementation code.