drill-tdd

drill-tdd is a skill for Claude Code from kucherenko/gangsta. It costs 34 tokens per session (2,117 once invoked), scanned A, original, MIT.

A test-driven development guide. Test-driven development means writing a test that fails first, then writing the smallest amount of code needed to make it pass, and finally improving the code.

In plain words
What is it for?
Use it for new features, bug fixes, refactoring, and behavior changes where tests should guide the implementation.
Why use it?
It prevents untested production changes by requiring the expected behavior to be demonstrated before implementation begins.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the gangsta plugin — 19 skills, 6 agents, 1 hook shipped together

Good fit Use it for new features, bug fixes, refactoring, and behavior changes where tests should guide the implementation.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/kucherenko/gangsta/drill-tdd
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.

Any agent
npx skills add kucherenko/gangsta --skill drill-tdd
Clone the repo
git clone --depth 1 https://github.com/kucherenko/gangsta

Made for: Claude Code.

Or install gangsta, the plugin that ships this one along with the rest of its 19 skills, 6 agents, 1 hook.

Wrote 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.

agentmods badge for drill-tdd

README.md
[![agentmods](https://agentmods.dev/badge/skills/kucherenko/gangsta/drill-tdd/github.svg)](https://agentmods.dev/skills/kucherenko/gangsta/drill-tdd)
Your own site
<a href="https://agentmods.dev/skills/kucherenko/gangsta/drill-tdd"><img src="https://agentmods.dev/badge/skills/kucherenko/gangsta/drill-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.

agentmods 80×15 button for drill-tdd

Your own site · 80×15
<a href="https://agentmods.dev/skills/kucherenko/gangsta/drill-tdd"><img src="https://agentmods.dev/badge/skills/kucherenko/gangsta/drill-tdd.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 34 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,117 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
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 5.1 $0.00034 $0.02117
Opus 5 $0.00017 $0.01059
Sonnet 5 $0.00007 $0.00423
Haiku 4.5 $0.00003 $0.00212

Measured 10d ago against content hash 0c9487893a86, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

drill-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 10d 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.

skills/drill-tdd/SKILL.md · 325 lines

How it starts

The opening of the file, as written. The whole thing — 325 lines — stays where its author put it; the contents beside it link to each section on GitHub.

The Drill: Test-Driven Development

Overview

Write the test first. Watch it fail. Write minimal code to pass.

Core principle: If you didn't watch the test fail, you don't know if it tests the right thing.

Violating the letter of the rules is violating the spirit of the rules.

When to Use

Always:

  • New features
  • Bug fixes
  • Refactoring
  • Behavior changes

Exceptions (ask the Don):

  • Throwaway prototypes
  • Generated code
  • Configuration files

Thinking "skip the Drill just this once"? Stop. That's rationalization.

The Iron Law (The Omerta of Testing)

NO PRODUCTION CODE WITHOUT A FAILING TEST FIRST

Write code before the test? Delete it. Start over.

No exceptions:

  • Don't keep it as "reference"
  • Don't "adapt" it while writing tests
  • Don't look at it
  • Delete means delete

Implement fresh from tests. Period.

Red-Green-Refactor

digraph tdd_cycle {
    rankdir=LR;
    red [label="RED\nWrite failing test", shape=box, style=filled, fillcolor="#ffcccc"];
    verify_red [label="Verify fails\ncorrectly", shape=diamond];
    green [label="GREEN\nMinimal code", shape=box, style=filled, fillcolor="#ccffcc"];
    verify_green [label="Verify passes\nAll green", shape=diamond];
    refactor [label="REFACTOR\nClean up", shape=box, style=filled, fillcolor="#ccccff"];
    next [label="Next", shape=ellipse];

    red -> verify_red;
    verify_red -> green [label="yes"];
    verify_red -> red [label="wrong\nfailure"];
    green -> verify_green;
    verify_green -> refactor [label="yes"];
    verify_green -> green [label="no"];
    refactor -> verify_green [label="stay\ngreen"];
    verify_green -> next;
    next -> red;
}

RED — Write Failing Test

Write one minimal test showing what should happen.

const result = await retryOperation(operation);

expect(result).toBe('success'); expect(attempts).toBe(3); });

Clear name, tests real behavior, one thing
</Good>

Read the full file on GitHub · 325 lines

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. 10d ago First seen · 325 lines · 34 tokens per session scan A 0c9487893a86

Subscribe to this mod's changes

drill-tdd is a skill published in the GitHub repository kucherenko/gangsta (81 stars, last pushed 26d ago), licensed MIT. It adds 34 tokens to every session and 2,117 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 2026-08-30.

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