Code Refactoring Skill

A systematic approach to refactoring code based on Martin Fowler's Refactoring: Improving the Design of Existing Code (2nd Edition). This skill emphasizes safe, incremental changes backed by tests.

"Refactoring is the process of changing a software system in such a way that it does not alter the external behavior of the code yet improves its internal structure.", Martin Fowler

Core Principles

1. Behavior Preservation: External behavior must remain unchanged
2. Small Steps: Make tiny, testable changes
3. Test-Driven: Tests are the safety net
4. Continuous: Refactoring is ongoing, not a one-time event
5. Collaborative: User approval required at each phase

Workflow Overview

Phase 1: Research & Analysis
    ↓
Phase 2: Test Coverage Assessment
    ↓
Phase 3: Code Smell Identification
    ↓
Phase 4: Refactoring Plan Creation
    ↓
Phase 5: Incremental Implementation
    ↓
Phase 6: Review & Iteration

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Phase 1: Research & Analysis

Objectives

• Understand the codebase structure and purpose
• Identify the scope of refactoring
• Gather context about business requirements

Questions to Ask User

Before starting, clarify:

1. Scope: Which files/modules/functions need refactoring?
2. Goals: What problems are you trying to solve? (readability, performance, maintainability)
3. Constraints: Are there any areas that should NOT be changed?
4. Timeline pressure: Is this blocking other work?
5. Test status: Do tests exist? Are they passing?

Actions

• Read and understand the target code
• Identify dependencies and integrations
• Document current architecture
• Note any existing technical debt markers (TODOs, FIXMEs)

Output

Present findings to user:

• Code structure summary
• Identified problem areas
• Initial recommendations
• Request approval to proceed

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Phase 2: Test Coverage Assessment