# Test Driven Development

Unified TDD skill with three input modes, from spec, from task, or from description.

- Repository: https://github.com/mikeyobrien/ralph-orchestrator (3190 stars)
- Category: Testing
- License: MIT
- Last updated: 2026-10-31
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add mikeyobrien/ralph-orchestrator --skill test-driven-development -g -a claude-code -y`
Codex: `npx skills add mikeyobrien/ralph-orchestrator --skill test-driven-development -g -a codex -y`
Cursor: `npx skills add mikeyobrien/ralph-orchestrator --skill test-driven-development -g -a cursor -y`
Gemini CLI: `npx skills add mikeyobrien/ralph-orchestrator --skill test-driven-development -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add mikeyobrien/ralph-orchestrator`

## Description

Unified TDD skill with three input modes, from spec, from task, or from description. Enforces test-first development using repository patterns, with proptest guidance and backpressure integration.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# Test-Driven Development

## Overview

One skill for all TDD workflows. Enforces test-first development using existing repository patterns. Three input modes handle different entry points, specs, task files, or ad-hoc descriptions, but the core cycle is always RED → GREEN → REFACTOR.

## Input Modes

Detect the input type and follow the corresponding mode:

### Mode A: From Spec (`.spec.md`)

Use when the input references a `.spec.md` file with Given/When/Then acceptance criteria.

1. **Locate and parse** the spec file, extract all Given/When/Then triples
2. **Generate one test stub per criterion** with `todo!()` bodies:
   ```rust
   /// Spec: <spec-file>, Criterion #<N>
   /// Given <given text>
   /// When <when text>
   /// Then <then text>
   #[test]
   fn <spec_name>_criterion_<N>_<slug>() {
       todo!("Implement: <then text>");
   }
   ```
3. **Verify stubs compile** but fail: `cargo test --no-run -p <crate>`
4. Proceed to the [TDD Cycle](#tdd-cycle) to make stubs pass

**Programmatic support:** `ralph_core::preflight::{extract_acceptance_criteria, extract_criteria_from_file, extract_all_criteria}` can parse criteria from spec files.

### Mode B: From Task (`.code-task.md`)

Use when the input references a `.code-task.md` file or a specific implementation task.

1. **Read the task** and identify acceptance criteria or requirements
2. **Discover patterns** (see [Pattern Discovery](#pattern-discovery))
3. **Design test scenarios** covering normal operation, edge cases, and error conditions
4. **Write failing tests** for all requirements before any implementation
5. Proceed to the [TDD Cycle](#tdd-cycle)

### Mode C: From Description

Use for ad-hoc tasks without a spec or task file.

1. **Clarify requirements** from the description
2. **Discover patterns** (see [Pattern Discovery](#pattern-discovery))
3. **Write failing tests** targeting the described behavior
4. Proceed to the [TDD Cycle](#tdd-cycle)

## Pattern Discovery

The rest: https://github.com/mikeyobrien/ralph-orchestrator/blob/HEAD/.claude/skills/test-driven-development/SKILL.md