Create tests that describe what legacy code actually does (not what it should do) as safety net before refactoring
Install
npx skills add spacholski1225/cc-config --skill 'Characterization Testing'npx skills add spacholski1225/cc-config --skill 'Characterization Testing' -a claude-code -gnpx skills add spacholski1225/cc-config --skill 'Characterization Testing' -a codex -ggemini skills install https://github.com/spacholski1225/cc-config.git --path skills/refactoring/characterization-testinggh skill install spacholski1225/cc-config 'Characterization Testing'git clone --depth 1 https://github.com/spacholski1225/cc-config /tmp/spacholski1225__cc-config
mkdir -p ~/.claude/skills ~/.agents/skills
cp -R /tmp/spacholski1225__cc-config/skills/refactoring/characterization-testing ~/.claude/skills/'Characterization Testing' # Claude Code
cp -R /tmp/spacholski1225__cc-config/skills/refactoring/characterization-testing ~/.agents/skills/'Characterization Testing' # Codex, Cursor, Gemini CLI, Copilot, OpenCode