Refactoring

Purpose

Systematically improve code maintainability using just coverage and just complexity to identify targets, then /plan and /work to execute refactoring safely.

Core principle: Never refactor without high test coverage. Tests prove behavior is preserved.

Software Laws

Apply these principles during refactoring:

• Gall's Law - Move from simple to complex incrementally
• Kernighan's Law - Simplify over-clever code
• Leaky Abstractions - Adjust/remove abstractions when they leak
• DRY - Eliminate duplication, single source of truth
• RED-GREEN-REFACTOR - Tests green before and after every change

Uses

Standard Interface: aug-just/justfile-interface (Level 0+1)

just coverage      # Find low-coverage areas (blocks if <96%)
just complexity    # Find high-complexity targets
just test         # Verify after each change
just check-all    # Quality gate before merge

Finding Refactoring Opportunities

Two approaches:

Autonomous (Recommended)

/refactor
# AI analyzes codebase
# Finds opportunities automatically
# Creates detailed GitHub issues

Then execute: /work <issue-number>

Manual

Use justfile commands to identify targets yourself.

Workflow

1. Identify Targets

Coverage gaps:

just coverage
# Fails if <96% - write tests before refactoring

Complexity hotspots:

just complexity
# Python: radon cc - look for C grade or complexity >10
# JavaScript: complexity report - functions >10
# Java: PMD report - methods >10

2. Plan Refactoring

Create issues for each refactoring target:

/plan Refactor user validation module - current complexity 15, target <10

This creates issues with:

• Clear acceptance criteria (complexity reduction measured)
• Technical notes (extract functions, simplify conditionals)
• Dependencies (test coverage prerequisites)

3. Execute Refactoring

/work 99  # Sequential execution with test verification

RED-GREEN-REFACTOR cycle per issue:

1. Run just test → Ensure green ✅
2. Make one small refactor
3. Run just test → Ensure still green ✅
4. Commit with clear message
5. Repeat until acceptance criteria met
6. Run just check-all before merge

4. Verify Improvements

just complexity  # Confirm reduction
just coverage    # Confirm maintained

Small Steps

Good refactoring commits:

refactor: extract validation from process_data
refactor: extract transformation from process_data
refactor: simplify conditionals with guard clauses

Never commit broken tests.

Coverage Threshold

Required before refactoring: 96% (aug-just baseline threshold)

If below threshold: Write tests first, then refactor

Common Patterns

Extract Function - Break large functions into single-purpose units Guard Clauses - Replace nested conditionals with early returns Extract Constants - Replace magic numbers with named constants Simplify Conditionals - Reduce boolean complexity

When NOT to Refactor

• Coverage <96% → Write tests first
• Unclear behavior → Study code first
• Behavior must change → That's a feature, not refactoring
• Time pressure → Do it right or not at all

Integration

This skill works with:

• aug-just plugin - Provides coverage/complexity/test commands
• /refactor - Autonomous analysis, creates refactoring issues (recommended)
• /plan - Manual planning for custom refactorings
• /work - Executes refactoring with test verification gates

Typical flow:

/refactor          # Find opportunities, create issues
/work 101          # Execute using this skill's guidance
/work 102          # Continue with next refactoring