35-testing-tdd

A rule set for test-driven development, or TDD, in which tests are written or updated before behavior changes are implemented. It also defines the verification commands required for the FF1-CLI project.

In plain words
What is it for?
Use it when changing FF1-CLI behavior to guide test-first development, refactoring with tests kept green, and running linting, tests, builds, and configuration-validation commands.
Why use it?
It catches regressions during development and prevents behavior changes from being handed off without tests and full checks. It makes failures part of the implementation work.

Cursor rule for Cursor

Install

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.

agentmods
npx agentmods add rules/feral-file/ff-cli/35-testing-tdd
Clone the repo
git clone --depth 1 https://github.com/feral-file/ff-cli

Made for: Cursor.

Per session 188 This file is loaded in full into every session.
When invoked 188 The same file — it is already loaded in full.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5 $0.00188 $0.00188
Opus 5 $0.00094 $0.00094
Sonnet 5 $0.00038 $0.00038
Haiku 4.5 $0.00019 $0.00019

Measured 2d ago against content hash b378b1a91abf, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

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 2d 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.

.cursor/rules/35-testing-tdd.mdc · 29 lines

What it actually says

Testing and Verification Rule

Required sequence

  1. Write or update focused tests first when behavior changes.
  2. Implement until tests pass.
  3. Refactor while keeping tests green.
  4. 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.

Changes

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.

  1. 2d ago First seen · 29 lines · 188 tokens per session scan A b378b1a91abf

Subscribe to this mod's changes

35-testing-tdd is a cursor rule published in the GitHub repository feral-file/ff-cli (5 stars, last pushed 14d ago), licensed MIT. It adds 188 tokens to every session, about $0.0009 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.