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Refactoring-aware code review

Code review, where developers manually inspect one another's code changes, improves software quality and transfers knowledge in a team. Unfortunately, tools that support code review treat behavior-preserving changes, or refactorings, and behavior-altering changes, or non-refactorings, the same way, so developers have to spend effort differentiating between the two before they can evaluate the impact of a change set. In this paper, we describe a formative study of 35 developers that motivates the need for separating refactorings from non-refactorings during code review. Then, we present a refactoring-aware code review tool, called ReviewFactor, that differentiates between refactoring and non-refactoring, and allows developers to focus on one of them at a time. Finally, a case study of two open source projects suggests that ReviewFactor detects refactorings in 39% of the commits, and identifies 4.6% of the total lines of code change as refactorings. Our results also show that the precision and recall of ReviewFactor's refactoring detection algorithm are 92.5% and 94.2%, respectively.