Getting it into your agent
It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.
git clone --depth 1 https://github.com/feral-file/ff-clinpx agentmods add rules/feral-file/ff-cli/35-testing-tddWrote 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/rules/feral-file/ff-cli/35-testing-tdd)<a href="https://agentmods.dev/rules/feral-file/ff-cli/35-testing-tdd"><img src="https://agentmods.dev/badge/rules/feral-file/ff-cli/35-testing-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/rules/feral-file/ff-cli/35-testing-tdd"><img src="https://agentmods.dev/badge/rules/feral-file/ff-cli/35-testing-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 | $0.00188 | $0.00188 |
| Opus 5.5 | $0.00075 | $0.00075 |
| Sonnet 5.5 | $0.00038 | $0.00038 |
| Haiku 4.5 | $0.00019 | $0.00019 |
Grade A, and why
35-testing-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 2mo 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.
What it actually says
Testing and Verification Rule
Required sequence
- Write or update focused tests first when behavior changes.
- Implement until tests pass.
- Refactor while keeping tests green.
- Run the full verification commands before handoff or completion.
Constraints
- Do not ship behavior changes without test coverage unless there is a clear, explicit reason.
- Prefer unit tests for business logic and targeted integration coverage for boundary behavior.
- Treat missing or failing tests as part of the work, not follow-up work.
Required verification commands
npm run lint:fix
npm test
npm run build
GROK_API_KEY=dummy node dist/index.js validate examples/sample-playlist.json
GROK_API_KEY=dummy node dist/index.js config validate
Fix failures and rerun until clean.
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.
- 2mo ago First seen · 29 lines · 188 tokens per session scan A b378b1a91abf
35-testing-tdd is a cursor rule published in the GitHub repository feral-file/ff-cli (5 stars, last pushed today), licensed MIT. It adds 188 tokens to every session, about $0.0008 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 cursor rules, from other repositories
mcpnuke-tests
Test conventions for mcpnuke — enforces TDD workflow.
debug-issue
When the user reports a bug, an error, or unexpected behavior. Enforces four structured phases — reproduction, failing test, root cause isolation, fix and verify — to stop guess-and-check loops.
common-testing
Testing requirements: 80% coverage, TDD workflow.
testing_rules
A testing guide covering TDD, where tests are written before code, and BDD, where expected behavior is described in Given-When-Then form.
tdd
Test-driven development — red-green-refactor cycle.
testing-standards
testing guidelines and expectations.