principle-refactoring

Refactor legacy code safely by writing characterization tests first to capture existing behavior, then applying small Fowler catalog moves while keeping tests green between commits. This ensures behavior preservation and prevents risky structural changes.

Map code smells to refactoring moves using smell-to-move mappings that translate issues like Long Method, Large Class, and Feature Envy into specific Fowler catalog sequences. This guides targeted structural improvements without altering functionality.

Characterization tests are safety nets you write before touching untested legacy code. You need them when refactoring code without coverage to turn unknown behavior into verified expectations before applying behavior-preserving moves.

Extract a function from a long method by applying the Extract Function refactoring in small, independently reviewable steps. Run tests after each move to stay green and ensure behavior preservation throughout the decomposition process.

Safety rules for behavior-preserving refactoring include separating refactors from features, keeping steps small, running tests between commits, and stopping on red flags like mixed intent or test manipulation to avoid altering behavior.

You can refactor untested code by introducing characterization tests first to document current behavior. This creates a verified safety net before applying Fowler catalog moves, ensuring legacy safety without changing behavior.