Detecting Behavioral Changes in Python Refactoring Implementations with Foundation Models

2026-08-10

AI Summary

This work addresses the risk that automated Python refactoring tools may inadvertently introduce behavioral changes, thereby compromising software reliability. To tackle this issue, the authors propose a novel approach that leverages foundation models as semantic oracles, integrated with Git diff parsing and automated validation, to detect behavior-altering refactorings. Applying this method to 217 refactoring instances produced by the Rope tool, the study uncovers 13 previously unknown defects, 12 of which have been acknowledged and fixed by the developers. This demonstrates the effectiveness of the technique in enhancing the trustworthiness and practical utility of automated refactoring tools.

Abstract

Python is a widely adopted programming language, valued for its simplicity and flexibility. However, automated refactoring for Python remains challenging, even though refactoring is an essential practice in software evolution aimed at improving internal code structure without changing external behavior. Understanding how behavioral changes are introduced during refactoring is crucial, as such issues can compromise software reliability and reduce developer productivity. We propose an approach based on a foundation model oracle that analyzes git-style diffs to identify behavioral changes introduced by Python refactorings. We evaluated our technique on Rope refactoring implementations, reusing 1,152 refactoring attempts from a prior study and analyzing 217 resulting transformation pairs with the oracle. Our model-based analysis uncovered 13 distinct bugs among the seven refactoring types studied. All reported bugs were submitted to the respective developers, and 12 of the 13 resulting issue reports were accepted according to issue-tracker evidence. These results highlight the need to improve the robustness of current Python refactoring tools to ensure the correctness of automated code transformations and support reliable software maintenance.

Problem

• behavioral changes
• Python refactoring
• automated code transformation
• software reliability
• refactoring tools

Innovation

• foundation models
• behavioral change detection
• Python refactoring
• code transformation validation
• automated software maintenance