Refactor

Improve code structure without changing external behavior.

Process

1. Understand — Read all related code, run existing tests
2. Plan — Identify what to change and why
3. Execute — Make changes incrementally
4. Verify — Run tests after each change

Common Refactoring Patterns

Extract

• Long function → smaller focused functions
• Repeated code → shared helper
• Magic numbers → named constants

Simplify

• Deep nesting → early returns / guard clauses
• Complex conditionals → descriptive functions
• Large classes → smaller focused classes

Rename

• Unclear names → descriptive names
• Inconsistent naming → consistent conventions

Reorganize

• Related functions scattered → grouped in modules
• Circular dependencies → dependency inversion

Rules

• Never change behavior — tests must pass before and after
• One refactoring type per commit
• If tests don't exist, write them first
• Don't refactor and add features in the same change