refactor

Refactor Skill

Step 1 — Understand the Goal

• What is wrong with the current code? (too long, duplicated, wrong layer, hard to test)
• What is the desired outcome? (extracted function, renamed variable, moved to correct layer)
• Are there tests in place? (if not, write characterization tests before refactoring)

Step 2 — Establish a Safety Net

• A characterization test captures current behavior (even if the behavior is wrong).
• It prevents accidental behavior changes during refactoring.

Step 3 — Apply Refactoring in Small Steps

• Extract function/method: identify a coherent chunk of logic with a clear purpose.
• Rename: choose a name that accurately describes the thing at the current abstraction level.
• Move to correct layer: domain logic in a controller → move to use case or domain service.
• Replace conditional with polymorphism: complex switch/if chains on type → strategy pattern.
• Introduce value object: raw primitive used to represent a domain concept → wrap it.
• Remove duplication: extract shared logic to a shared function; do not abstract prematurely.

Step 4 — Verify Behavior is Unchanged

• All tests pass.
• The public API (exported signatures) is unchanged.
• No new dependencies introduced.

Step 5 — Summarize

## Refactor Summary

**What changed**: [List of moves applied]
**Why**: [The design problem that was addressed]
**Tests**: [Pass / added N new characterization tests]
**Breaking changes**: None (internal only)