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/danielvm-git/bigpowersnpx agentmods add rules/danielvm-git/bigpowers/develop-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/danielvm-git/bigpowers/develop-tdd)<a href="https://agentmods.dev/rules/danielvm-git/bigpowers/develop-tdd"><img src="https://agentmods.dev/badge/rules/danielvm-git/bigpowers/develop-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/danielvm-git/bigpowers/develop-tdd"><img src="https://agentmods.dev/badge/rules/danielvm-git/bigpowers/develop-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 | $0.00034 | $0.03612 |
| Opus 5.5 | $0.00014 | $0.01445 |
| Sonnet 5.5 | $0.00007 | $0.00722 |
| Haiku 4.5 | $0.00003 | $0.00361 |
Grade A, and why
develop-tdd scanned grade A with 1 finding 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.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
fetch: (endpoint, options) => fetch(endpoint, options), How it starts
The opening of the file, as written. The whole thing — 416 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Develop TDD
HARD GATE — Do NOT proceed if on
mainormaster. Runkickoff-branchfirst to create a feature branch or worktree.HARD GATE — Do NOT write code before you have a plan. New feature:
plan-work→ epic capsule tasks. Bug:investigate-bug→specs/bugs/BUG-*.md(or usefix-bugorchestrator).RECURSIVE DISCIPLINE — This lifecycle applies to EVERY task, including updating these skills. Never skip planning because a task is "meta" or "just documentation."
Philosophy
Tests verify behavior through public interfaces, not implementation details. A good test reads like a specification. See REFERENCE.md for the horizontal-slice anti-pattern and TDD phase detail.
Red Flags
If you catch yourself thinking these, stop and reconsider — you are likely deviating from production-grade craft.
| Red Flag | Reality |
|---|---|
| "This is too simple to need tests." | Simple code is where bugs hide. If it's simple, the test is cheap. |
| "I'll refactor this later." | "Later" is when technical debt becomes bankruptcy. Refactor while Green. |
| "The tests are already comprehensive." | If you're adding behavior, you need a new test. Coverage ≠ Correctness. |
| "I'm just fixing a small bug." | Small bugs often indicate deep interface flaws. Investigate root cause. |
| "I need to mock this internal class." | Mocking internals couples tests to implementation. Mock only I/O. |
| "This refactor is out of scope." | Leave the code cleaner than you found it (Boy Scout Rule). |
| "Preflight failed but it's unrelated." | Always Green: any reproducible gate failure routes quick-fix → fix-bug before forward work. Session boundaries do not waive Preflight. |
| "I'll note the red gate and continue." | Narrating a failure is banned. fix-or-log is mandatory per CONVENTIONS § Discovered Defects. |
Workflow
Timing:
bash scripts/bp-timing.sh start develop-tddat invocation;bash scripts/bp-timing.sh end develop-tddbefore handoff.
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 · 416 lines · 34 tokens per session scan A a0f0b87c0623
develop-tdd is a cursor rule published in the GitHub repository danielvm-git/bigpowers (267 stars, last pushed 27d ago), licensed MIT. It adds 34 tokens to every session and 3,612 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
Other cursor rules, from other repositories
testing
Vitest, React Testing Library, and Playwright testing standards. Enforces TDD/BDD, test pyramid, zero brittle mocks, and complete assertion coverage.
bug-fix-tdd-guard
A rule for fixing software bugs with test-driven development, or TDD: first reproduce the bug, then write a test that fails, then make the smallest code change that passes it, and finally run the full checks.
refactoring
Refactoring: systematic approach, extract/inline, guard clauses, early returns.
tdd
Test-driven development — red-green-refactor cycle.
testing-and-safety
TDD bias; no secrets in code; new logic needs unit tests.
mcpnuke-tests
Test conventions for mcpnuke — enforces TDD workflow.