Breaking the Barriers to Successful Refactoring: Observations and Tools for Extract Method

Refactoring is the process of changing the structure of code without changing its behavior. Refactoring can be semi-automated with tools, which should make it easier for programmers to refactor quickly and correctly. However, we have observed that many tools do a poor job of communicating errors triggered by the refactoring process and that programmers using them sometimes refactor slowly, conservatively, and incorrectly. In this paper we characterize problems with current refactoring tools, demonstrate three new tools to assist in refactoring, and report on a user study that compares these new tools against existing tools. The results of the study show that speed, accuracy, and user satisfaction can be significantly increased. From the new tools we induce a set of usability recommendations that we hope will help inspire a new generation of programmer-friendly refactoring tools.