How Much Can a Behavior-Preserving Changeset Be Decomposed into Refactoring Operations?

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Abstract

Developers sometimes mix behavior-preserving modifications, such as refactorings, with behavior-altering modifications, such as feature additions. Several approaches have been proposed to support understanding such modifications by separating them into those two parts. Such refactoring-aware approaches are expected to be particularly effective when the behavior-preserving parts can be decomposed into a sequence of more primitive behavior-preserving operations, such as refactorings, but this has not been explored. In this paper, as an initial validation, we quantify how much of the behavior-preserving modifications can be decomposed into refactoring operations using a dataset of functionally-equivalent method pairs. As a result, when using an existing refactoring detector, only 33.9% of the changes could be identified as refactoring operations. In contrast, when including 67 newly defined functionally-equivalent operations, the coverage increased by over 128%. Further investigation into the remaining unexplained differences was conducted, suggesting improvement opportunities.

BibTeX

@inproceedings{someya-icsme2025,
    author = {Kota Someya and Lei Chen and Michael J. Decker and Shinpei Hayashi},
    title = {How Much Can a Behavior-Preserving Changeset Be Decomposed into Refactoring Operations?},
    booktitle = {Proceedings of the 41st IEEE International Conference on Software Maintenance and Evolution},
    pages = {809--814},
    doi = {10.1109/ICSME64153.2025.00084},
    year = 2025,
}