SKILL: Test-Driven Development (TDD)

Purpose: Execute TDD Red-Green-Refactor cycle for feature implementation Target: Coder teammates implementing features with test-first methodology in Agent Teams ⚠️ Teammates Only: This skill is for coder teammates in Agent Teams. Team Lead delegates via teammate spawn.

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Quick Start

When to Use This Skill

• Implement new feature with test coverage
• Fix bug with regression tests
• Refactor code with test safety net

Quick Reference

# Red: pytest tests/test_feature.py -k "SC-1"  # FAIL
# Green: [Implement feature]
# Refactor: [Refactor code]
# Verify: pytest  # ALL PASS

What This Skill Covers

In Scope

• Red-Green-Refactor cycle execution
• Test-first development methodology
• Minimal implementation for Green phase

Out of Scope

• Test framework selection → @.claude/skills/tdd/REFERENCE.md
• Coverage thresholds → @.claude/skills/ralph-loop/SKILL.md
• Code quality standards → @.claude/skills/vibe-coding/SKILL.md

Core Concepts

The TDD Cycle: Red-Green-Refactor

Phase 1: Red - Write Failing Test

def test_add_two_numbers():
    result = calculator.add(2, 3)
    assert result == 5

Run test → Confirm it FAILS (❌)

Phase 2: Green - Minimal Implementation

def add(a, b):
    return a + b  # Just enough to pass

Run test → Confirm it PASSES (✅)

Phase 3: Refactor - Improve Quality

def add(a: int, b: int) -> int:
    """Add two integers with type safety."""
    return a + b

Run ALL tests → Confirm ALL PASS (✅)

Why TDD Matters

• Tests drive design: API designed from usage perspective
• Regression safety: Refactor without fear
• Living documentation: Tests show intended behavior
• Fast feedback: Catch issues immediately

Further Reading

Internal: @.claude/skills/tdd/REFERENCE.md - Advanced TDD concepts, patterns, and examples | @.claude/skills/ralph-loop/SKILL.md - Autonomous completion loop | @.claude/skills/vibe-coding/SKILL.md - Code quality standards | @.claude/skills/tdd/REFERENCE.md - Test framework detection

External: Test-Driven Development by Kent Beck | Growing Object-Oriented Software, Guided by Tests