Refactor safely by name: a catalogue of the refactorings that come up in practice (extract function or module, inline, rename, replace conditional with polymorphism or lookup, introduce parameter object, replace flag argument, split phase, move function, encapsulate collection, strangler for large rewrites), each with when to apply it, the mechanical steps that keep the code working at every step, and the test to run between steps. Use when code is hard to change, before adding a feature to a tangled area, or when a reviewer asks for a structure change without saying how.
