# Test Driven Development

> Test-first development practice where test specifications are written before production code, integrated into plan tasks as mandatory first sub-steps.

- Skill: `a5c-ai/test-driven-development-2` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add a5c-ai/test-driven-development-2`
- Raw SKILL.md: https://api.skillmd.com/api/skills/a5c-ai/test-driven-development-2/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: a5c-ai (https://skillmd.com/u/a5c-ai)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/a5c-ai/test-driven-development-2

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- During implementation (write tests before code)
- When verifying step completion

## Process

1. **Specify tests first** - Define inputs, expected outputs, edge cases
2. **Write test code** - Create automated tests matching specification
3. **Implement production code** - Write code that passes the tests
4. **Verify** - Run tests and confirm all pass

## Test Categories

- **Unit tests**: Isolated function/method testing
- **Integration tests**: Cross-component interaction testing
- **Manual verification**: Human-performed checks when automation is impractical

## Key Rules

- Never combine test writing and implementation into a single step
- Every task with code changes must have associated tests
- Tests must be runnable and produce clear pass/fail results
- Edge cases must be explicitly considered

## Tool Use

Integrated into `methodologies/rpikit/rpikit-plan` and `methodologies/rpikit/rpikit-implement`