name: Refactor description: Improve code design without changing behaviour. Use for the REFACTOR phase of XP workflow. All tests must pass before and after.

Refactor

Core Rules (Non-Negotiable)

1. NEVER change behaviour — refactoring preserves existing functionality
2. All tests must pass before and after refactoring
3. Small incremental changes — one transformation at a time
4. Run tests after every change — catch regressions immediately

The Refactor Cycle

✅ VERIFY   → Run all tests, confirm green state
🔍 ANALYSE  → Identify code smell or improvement opportunity
🔵 REFACTOR → Apply ONE transformation
✅ VERIFY   → Run all tests, confirm still green
🔁 REPEAT   → Continue until goal achieved

Goals & Techniques

Code Smells to Address

• Duplication — same code in multiple places
• Long methods — do too much, hard to understand
• Large classes — too many responsibilities
• Long parameter lists — difficult to call correctly
• Feature envy — method uses another class more than its own
• Primitive obsession — using primitives instead of small objects

What Refactoring Is NOT

• Adding new features
• Fixing bugs (unless the fix is purely structural)
• Changing external APIs

Announcing Changes

🔵 REFACTOR → [smell]: [transformation]

Examples:

• 🔵 REFACTOR → duplication: Extract method calculateTotal
• 🔵 REFACTOR → long method: Split processOrder into validate and execute

Safety Checklist

Before starting:

• All tests pass
• Understand the code being refactored

After each change:

• Tests still pass
• Behaviour unchanged
• Code is cleaner/clearer