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

The Iron Law mandates that no production code can be written without a failing test first. If code is written before a test, it must be deleted and rewritten from scratch starting with the test.

Why does the skill insist on watching a test fail first?

Watching a test fail confirms that the test is actually evaluating the new behavior and isn't passing accidentally due to existing logic or a configuration error.

Does this skill support Python and JavaScript?

Yes, it is language-agnostic and includes specific implementation patterns and commands for frameworks like Jest, Vitest, Bun, and Pytest.

Can I use this skill for refactoring?

Yes. The skill includes a dedicated 'Refactor' phase that occurs only after a test is green, ensuring that code cleanup doesn't break existing functionality.

Test-Driven Development (TDD)

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

bySiTaggart

Security & Testing

Enforces a strict Red-Green-Refactor workflow to ensure high-quality code through test-first implementation.

About

The Test-Driven Development skill transforms Claude into a disciplined TDD practitioner, strictly adhering to the 'Iron Law' of writing failing tests before any production code. It guides the development process through a rigorous cycle: writing a minimal failing test, verifying the failure, implementing the simplest possible solution to pass, and refactoring for clean code. By preventing common rationalizations and ensuring systematic verification at every step, this skill helps developers build more reliable, maintainable, and bug-free software architectures.

Key Features

Multi-language support for Jest, Pytest, Bun, and more
Built-in TDD verification checklist for code completion
Automatic purging of production code written without preceding tests
Strict enforcement of the Red-Green-Refactor development cycle
Mandatory failure verification to prevent false-positive tests
0 GitHub stars

Use Cases

Implementing new features with 100% test coverage from day one
Safe refactoring of legacy code by maintaining green test states
Systematically reproducing and fixing bugs using failing test cases

About

Key Features

Multi-language support for Jest, Pytest, Bun, and more
Built-in TDD verification checklist for code completion
Automatic purging of production code written without preceding tests
Strict enforcement of the Red-Green-Refactor development cycle
Mandatory failure verification to prevent false-positive tests
0 GitHub stars

Use Cases

Implementing new features with 100% test coverage from day one
Safe refactoring of legacy code by maintaining green test states
Systematically reproducing and fixing bugs using failing test cases