Refactor

/refactor

Safely refactor code with test-driven approach.

Usage

/refactor <target> [--scope <scope>] [--dry-run]

Arguments

• target: File, function, or pattern to refactor
• --scope: Limit refactoring scope (function, file, module)
• --dry-run: Show planned changes without executing

Instructions

When this skill is invoked:

Agent Behavior (Codex-Max Pattern)

Autonomy:

• Complete the refactoring end-to-end
• Run tests before, during, and after changes
• Verify no behavior changes unless explicitly requested

Safety:

• NEVER refactor without tests in place
• Create tests first if missing
• Make incremental changes with verification

Quality:

• Follow DRY principle
• Improve code clarity
• Maintain or improve test coverage

Refactoring Process

1. Verify tests exist:

   {test_command} tests/ --collect-only
   

   If tests don't exist for the target:

   • Create tests first
   • Verify tests pass with current implementation
   • Document existing behavior

2. Run tests to establish baseline:

   {test_coverage_command}
   

   Record:

   • Number of passing tests
   • Coverage percentage
   • Test duration

3. Plan the refactoring:

   • Identify code smells or issues
   • Determine refactoring strategy
   • List files that will be affected
   • If --dry-run, present plan and stop

4. Execute refactoring in small steps: For each change:

   • Make the change
   • Run affected tests
   • Verify tests still pass
   • If tests fail, rollback and investigate

5. Verify final state:

   {test_coverage_command}
   

   Ensure:

   • ✅ All tests pass
   • ✅ Coverage not decreased
   • ✅ No new linting errors
   • ✅ Type checking passes

6. Present changes:

   • List all modified files
   • Summarize improvements
   • Show before/after metrics

Common Refactoring Patterns

Extract Function/Method:

# Before
def process():
    # 50 lines of code

# After
def process():
    step1()
    step2()
    step3()

Remove Duplication:

# Before: Same code in 3 places
# After: Single shared function

Simplify Conditionals:

# Before
if x and y and z:
    if a or b:
        ...

# After
if should_process(x, y, z, a, b):
    ...

Rename for Clarity:

# Before
def proc(d):

# After
def process_user_data(user_data):

Safety Rules

1. Never refactor without tests
2. Make small, incremental changes
3. Run tests after each change
4. Preserve existing behavior (unless explicitly changing it)
5. Update documentation if interfaces change
6. Keep commits atomic (one logical change per commit)

Example Output

$ /refactor src/{project}/services/user --scope module

🔄 Refactoring: src/{project}/services/user

📋 Pre-refactor state:
- Tests: 24 passing
- Coverage: 95%
- Duration: 1.2s

📝 Planned changes:
1. Extract duplicate validation logic → shared validator
2. Rename process() → process_user_request()
3. Simplify nested conditionals in update()

🔧 Executing refactoring...

Step 1: Extract validation logic
  ✅ Tests pass (24/24)

Step 2: Rename process()
  ✅ Tests pass (24/24)

Step 3: Simplify conditionals
  ✅ Tests pass (24/24)

📋 Post-refactor state:
- Tests: 24 passing
- Coverage: 96% (+1%)
- Duration: 1.1s (-0.1s)

✅ Refactoring complete!

Changes made:
- src/{project}/services/user: Simplified, renamed functions
- src/{project}/utils/validators: New shared validation module
- tests/unit/test_user: Updated imports

Commit suggestion:
git commit -m "refactor(user): extract validation, improve naming"