Making Program Refactoring Safer

Developers rely on compilation, test suites, and tools to preserve observable behavior during refactoring. However, most refactoring tools don´t implement all the preconditions that guarantee refactoring correctness because formally identifying them is cost-prohibitive. Therefore, these tools could perform nonbehavior-preserving transformations. The authors present a tool for improving safety during refactoring that automatically generates a test suite suited for detecting behavioral changes. They used this tool to evaluate seven real case study refactorings (from 3 to 100 KLOC).