refactoring-patternslisted

# Refactoring Patterns Skill ## When to Use Invoke this skill when: - Code smells are detected (long functions, duplicated logic, shotgun surgery) - Before making major structural changes to existing code - During tech debt sprints or cleanup tasks - A function exceeds 30 lines and needs decomposition - Renaming, moving, or reorganizing code across files or packages ## The Golden Rule ``` Tests green -> Refactor -> Tests green ``` Never refactor code that lacks test coverage. If tests don't exist, write them first (characterization tests that capture current behavior), then refactor. ## Safe Refactoring Steps 1. **Verify tests pass** before touching anything. Run the full suite for the affected area. 2. **Make one refactoring move at a time.** Never combine multiple refactorings in a single change. 3. **Run tests after each move.** If anything fails, you know exactly which move broke it. 4. **Commit after each successful step.** Small commits make `git bisect` possible and rollback trivial. 5. **If tests fail, revert the last move.** Do not debug forward -- undo and try a different approach. ``` [tests pass] -> extract method -> [tests pass] -> commit -> rename variable -> [tests pass] -> commit -> move to new file -> [tests pass] -> commit -> [tests FAIL] -> git revert -> rethink ``` ## Common Patterns ### Extract Method **Smell:** Function too long, or comments explaining what a block does. **Action:** Pull the block into a