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Automated testing of refactoring engines

TitleAutomated testing of refactoring engines
Publication TypeConference Paper
Year of Publication2007
AuthorsDaniel, B., D. Dig, K. Garcia, and D. Marinov
Conference NameProceedings of the the 6th joint meeting of the European software engineering conference and the ACM SIGSOFT symposium on the foundations of software engineering - ESEC-FSE '07
Date Published09/2007
PublisherACM Press
Conference LocationDubrovnik, Croatia
ISBN Number9781595938114

Refactorings are behavior-preserving program transformations that improve the design of a program. Refactoring engines are tools that automate the application of refactorings: first the user chooses a refactoring to apply, then the engine checks if the transformation is safe, and if so, transforms the program. Refactoring engines are a key component of modern IDEs, and programmers rely on them to perform refactorings. A bug in the refactoring engine can have severe consequences as it can erroneously change large bodies of source code.

We present a technique for automated testing of refactoring engines. Test inputs for refactoring engines are programs. The core of our technique is a framework for iterative generation of structurally complex test inputs. We instantiate the framework to generate abstract syntax trees that represent Java programs. We also create several kinds of oracles to automatically check that the refactoring engine transformed the generated program correctly. We have applied our technique to testing Eclipse and NetBeans, two popular open-source IDEs for Java, and we have exposed 21 new bugs in Eclipse and 24 new bugs in NetBeans.