Why is watching the test fail (RED phase) mandatory?

Watching a test fail proves that the test is actually checking the intended behavior. If a test passes immediately, it may be testing the wrong thing or verifying existing behavior instead of new requirements.

How does this skill handle bug fixes?

It requires writing a failing test that reproduces the bug before any fix is implemented. This proves the fix works and prevents future regressions of the same issue.

What is the 'Iron Law' of this TDD skill?

The Iron Law dictates that no production code is written without a failing test first. If code is accidentally written before the test, it must be deleted and restarted to ensure the test is actually verifying the logic.

What happens during the REFACTOR phase?

Once the code is 'Green' (passing), it is cleaned up for readability, duplication is removed, and helpers are extracted. No new behavior is added during this phase, and tests must remain passing throughout.

Test-Driven Development (TDD)

Name: Test-Driven Development (TDD)
Author: astrosteveo

byastrosteveo

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Security & Testing

Enforces a strict Red-Green-Refactor workflow to ensure high-quality, verified code production through test-first development.

This skill provides Claude with a rigorous framework for Test-Driven Development (TDD), emphasizing the 'Iron Law' that no production code should be written without a preceding failing test. It guides Claude through the standard Red-Green-Refactor cycle, helping to define minimal test cases, verify failures, implement the simplest passing solutions, and perform safe refactoring. By using this skill, developers can reduce technical debt, prevent regressions, and ensure that all new features and bug fixes are backed by reliable, automated documentation of behavior.

Key Features

011 GitHub stars

02Guidance on identifying and stopping common TDD rationalizations

03Comprehensive verification checklist for TDD compliance

04Mandatory verification of test failure (Red) before implementation

05Strict enforcement of the Red-Green-Refactor development cycle

06Minimal code implementation focus to prevent over-engineering

Use Cases

01Performing safe code refactoring while maintaining existing system functionality

02Implementing new software features with high reliability and verified behavior

03Fixing software bugs by reproducing them with failing tests before patching

What are Skills?·How to Install

Install with 🐟 Skill.Fish

npx skillfish add astrosteveo/marketplace test-driven-development

For use in Claude.ai and ChatGPT

Download Skill