Why does this skill require the test to fail first?

If you don't watch a test fail, you can't be sure it's actually testing the right thing or that it wouldn't pass regardless of your code. Verifying the 'RED' state proves the test is valid.

Is this skill compatible with my programming language?

Yes. While the process is standardized, it integrates with language-specific test runners like Cargo for Rust, XCTest for Swift, and Jest/Vitest for TypeScript.

Can I keep my pre-written code as a reference?

No. The skill follows a strict 'delete and restart' rule for code written before tests to prevent implementation bias and ensure the tests drive the design, not the other way around.

What happens if my test passes immediately?

A test passing immediately indicates you are either testing existing behavior or your test is flawed. You must fix the test or the environment until you achieve a meaningful failure.

Test-Driven Development

Name: Test-Driven Development
Author: withzombies

bywithzombies

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セキュリティとテスト

Enforces a rigorous RED-GREEN-REFACTOR cycle to ensure every line of production code is verified by a failing test first.

The Test-Driven Development skill transforms Claude into a disciplined software engineer by mandating the RED-GREEN-REFACTOR workflow. It prevents the common mistake of writing tests after implementation, instead requiring a verified failing test before any production code is written. This approach ensures that your test suite actually catches bugs, encourages simpler software design through 'testability' signals, and provides a safety net for continuous refactoring. By following the 'Iron Law' of TDD, this skill helps developers build more reliable, decoupled, and maintainable systems.

主な機能

01Mandatory 'Verify RED' phase to confirm test validity

02Strict enforcement of the RED-GREEN-REFACTOR cycle

03Focus on minimal code implementation for the GREEN phase

04Automatic design feedback by identifying hard-to-test code

05Detection and prevention of 'test-after' development patterns

0613 GitHub stars

ユースケース

01Implementing new features with guaranteed 100% functional coverage

02Safely refactoring complex logic while maintaining green test states

03Fixing bugs by first creating a failing regression test to reproduce the issue

What are Skills?·How to Install

Install with 🐟 Skill.Fish

npx skillfish add withzombies/hyperpowers test-driven-development

For use in Claude.ai and ChatGPT

Download Skill