refactor-safely

Refactor Ruby on Rails codebases in small steps with characterization tests.

22|6|Updated Mar 11, 2026

Search Tags:#testing #refactor #rails #guardrails #stepwise #characterization-tests

Ready to run

npx skills add https://github.com/igmarin/rails-agent-skills --skill refactor-safely-igmarin

💬 Prompt for ChatGPT / Claude Chat▼

Please help me install this Agent Skill.
Skill: refactor-safely
Source: https://github.com/igmarin/rails-agent-skills/tree/main/refactor-safely
Command: npx skills add https://github.com/igmarin/rails-agent-skills --skill refactor-safely-igmarin

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve?

Use when the task is to change structure without changing behavior. This skill helps you make safe, small steps to refactor code, harness characterization tests, and separate design improvements from functional changes.

Core Features & Use Cases

Define stable behavior with characterization tests
Extract, rename, or reorganize code in small steps
Verify progressively with tests and maintain compatibility

Quick Start

Define the stable behavior with characterization tests first, then perform the smallest safe refactor steps and verify tests after each step.

Frequently Asked Questions about refactor-safely

High-intent search queries and answers about installing and using this skill.

FAQPage Schema

How do I refactor a Rails codebase without changing its behavior?▼

You can refactor Rails safely by defining stable behavior with characterization tests first, then making the smallest structural changes step by step and verifying tests after each step to ensure behavior is preserved.

What are characterization tests and when do I need them for a refactor?▼

Characterization tests define the current stable behavior of your code before you refactor. You need them when changing structure without changing behavior, ensuring that incremental refactors like extracting services do not alter functionality.

How do I extract services or rename abstractions in Rails incrementally?▼

Extract services or rename abstractions by making small, stepwise structural changes while preserving public interfaces until callers are migrated. Run characterization tests after every step to verify progressive compatibility and unchanged behavior.

Does stepwise refactoring work for reorganizing modules in Ruby on Rails?▼

Stepwise refactoring works for reorganizing Rails modules by separating design improvements from functional changes. It maintains a clear separation of behavior and structure, verifying progressive compatibility with tests after each small structural step.

What are the limitations of using guardrails for Rails refactoring?▼

Guardrails for refactoring require maintaining a clear separation of behavior and structure, and you must preserve public interfaces until callers are migrated. It is limited to structural changes and cannot be used for functional modifications.