Making Program Refactoring Safer
Resumo
Developers rely on compilation, test suite and tools to preserve observable behavior during refactorings. However, most of the refactoring tools do not implement all preconditions that guarantee behavioral preservation, since formally identifying them is cost-prohibitive. Therefore, these tools may change the behavior of the user’s code. We propose two approaches for making program refactoring safer. We present an approach and its implementation (SAFEREFACTOR) useful for improving the developer’s confidence that the refactoring was correctly applied. It analyzes a transformation and generates tests specific for detecting behavioral changes. Moreover, we propose an approach to help refactoring tool developers to test their implementations. This approach evaluates an implementation by automatically generating programs (test inputs), and checking the results with SAFEREFACTOR. We evaluated SAFEREFACTOR in transformations applied to seven real programs ranging from 3 to 100 KLOC. In one of them (JHotDraw), we identified a behavioral change that was not revealed so far. On the other hand, we evaluated the second approach by testing 22 refactoring implementations in two Java refactoring tools: the Eclipse Refactoring Module and the JastAdd Refactoring Tool. We analyzed more than 80K transformations, and identified 67 bugs.
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