---
name: test-driven-development
description: Enforce RED→GREEN→REFACTOR micro-cycles and keep diffs minimal
version: 0.1.0
tags: [testing, quality]
triggers:
  - tdd
  - tests first
  - failing test
---

# Test-Driven Development

## Purpose
Bias implementation to tests-first and small, verifiable changes.

## Behavior
1. RED: scaffold 1–3 failing tests targeting the smallest slice.
2. GREEN: implement the minimum code to pass.
3. REFACTOR: improve names/structure with tests green.
4. Repeat in tiny increments until task acceptance criteria are met.

## Guardrails
- Block large edits unless a failing test exists.
- Prefer small diffs spanning ≤3 files.
- Keep test names explicit and deterministic.

## Output Style
- `bullet-points` for steps; `markdown-focused` for code blocks.

## Integration
- `/lazy task-exec` implementation phase; Coder/Tester agents.

## Example Prompt
> Apply TDD to implement input validation for prices.