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 agentmods add skills/pekral/cursor-rules/test-driven-developmentnpx skills add pekral/cursor-rules --skill test-driven-developmentgit clone --depth 1 https://github.com/pekral/cursor-rulesWrote 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/pekral/cursor-rules/test-driven-development)<a href="https://agentmods.dev/skills/pekral/cursor-rules/test-driven-development"><img src="https://agentmods.dev/badge/skills/pekral/cursor-rules/test-driven-development.svg" alt="Measured on agentmods" 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 | $0.00031 | $0.01459 |
| Opus 5 | $0.00015 | $0.00730 |
| Sonnet 5 | $0.00006 | $0.00292 |
| Haiku 4.5 | $0.00003 | $0.00146 |
Grade A, and why
test-driven-development 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 today.
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 — 111 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Constraints
- Apply
@rules/php/core-standards.mdc - Apply
@rules/code-testing/general.mdc - If the current project uses Laravel, also apply
@rules/laravel/laravel.mdc,@rules/laravel/architecture.mdc,@rules/laravel/filament.mdc, and@rules/laravel/livewire.mdc - Follow test conventions from
@skills/create-test/SKILL.md
Core principle
If you did not watch the test fail, you do not know whether it tests the right thing.
Iron law
NO PRODUCTION CODE WITHOUT A FAILING TEST FIRST
Use when
- Implementing a new feature
- Fixing a bug
- Changing behavior
- Refactoring code that should remain behaviorally stable
Read, Map & Verify before the first RED (mandatory pre-flight)
Reading, mapping, and verifying come first; implementing comes last. This pre-flight is blocking — do not add or modify a single line of production code until all three steps pass, and never act on an assumption you have not confirmed by reading the code.
- Read — open and read the actual target files and the code they depend on (callers, called methods, related tests, configuration). Confirm what the code does by reading it, not by guessing from names or the assignment description.
- Map — map the change's blast radius: every call site, caller, data-flow path, and existing test that the behavior touches, plus the conventions and helpers already in the codebase to reuse instead of reinventing.
- Verify — check your assumptions against the real code and its observed behavior (reproduce the current behavior so the first RED test asserts the real gap). If what you read contradicts the assignment framing, stop and surface the discrepancy instead of writing a test on a wrong premise.
Only after Read, Map, and Verify are complete may the first RED test be written.
Pre-flight (mandatory before the first RED)
Before writing the first failing test, run @skills/prepare-issue-context/SKILL.md with MODE=tdd and the assignment reference, scoped to the scenario(s) the upcoming RED step will cover. The skill seeds the development database with the records the failing test will depend on and captures a reproduction record (entry point + inputs + observed output) that becomes the arrange block of the first test. If the skill returns blocked: <count> open gap(s), stop and surface the gaps — writing a RED test against missing or guessed fixtures is the most common cause of stub-grade tests that drift from real behavior.
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.
- today First seen · 111 lines · 31 tokens per session scan A a16e3c7204fa
test-driven-development is a skill published in the GitHub repository pekral/cursor-rules (6 stars, last pushed 3d ago), licensed MIT. It adds 31 tokens to every session and 1,459 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 2026-09-03.
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