Refactoring Plan Skill

Refactoring means improving structure without changing behavior — and the danger is doing it in one big risky sweep. This skill plans the opposite: a safety net first, then a sequence of small, behavior-preserving steps, each leaving the code green and committable. It separates refactoring from feature work, so you're never doing both at once.

Required Inputs

Ask for these only if they aren't already provided:

• The code & the pain — what's being refactored and why (hard to change, duplicated, slow, untestable).
• Test coverage — what tests exist around it (and the framework). If none, that's step zero.
• The goal — the target structure or what you want to make easy next (e.g. "so I can add payment provider #2").
• Constraints — what must not change (public API, behavior, performance), time budget.

Output Format

Refactoring plan: target]

Why & goal — the current pain in one line, and what "better" enables.

Safety net (do first) — the tests that must exist before touching anything. If coverage is thin, add characterization tests that pin current behavior (even bugs) so you'd notice any change. Don't refactor untested code blind.

Target structure — a short sketch of where you're going (the shape, the seams, the names).

Steps (small & sequenced) — each step is behavior-preserving and independently committable:

| # | Step | Refactoring move | Stays green by | Commit after | |---|---|---|---|---| | 1 | … | (extract function / rename / introduce interface / move) | run tests | ✅ |

Order them so risk drops early and each step is reversible.

Definition of done — behavior identical (tests still green), the goal structure reached, no feature changes smuggled in.

Quality Checks

• ] A safety net (existing or characterization tests) is established before any change
• ] Every step is behavior-preserving and independently committable
• ] Steps are small and sequenced so the code is green throughout
• ] Refactoring is kept separate from behavior/feature changes
• ] The target structure is explicit and tied to what it makes easier next

Anti-Patterns

• ] Do not refactor and add features in the same commit — separate them
• ] Do not start without tests — add characterization tests first if coverage is thin
• ] Do not plan a big-bang rewrite — sequence small, reversible steps
• ] Do not change behavior and call it refactoring — behavior must stay identical
• ] Do not skip running tests between steps — that's the whole safety mechanism

Based On

Refactoring discipline (Martin Fowler): behavior-preserving transformations, characterization tests, small steps.