refactor

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

Goal	Techniques
Eliminate duplication	Extract method, extract variable, pull up method
Improve clarity	Rename, inline temp, introduce explaining variable
Simplify conditionals	Decompose conditional, consolidate conditional
Improve structure	Extract class, move method, replace inheritance with delegation

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