Exploring the Differences between Plausible and Correct Patches at Fine-Grained Level

Test-based automated program repair techniques use test cases to validate the correctness of automatically-generated patches. However, insufficient test cases lead to the generation of incorrect patches, i.e., passing all the test cases, however are incorrect. In this work, we present an exploratory study to understand what are the runtime behaviours are being modified by automatically-generated plausible patches, and how such modifications of runtime behaviours are different from those by correct patches. We utilized an off-the-shelf invariant generation tool to infer an abstraction of runtime behaviours and computed the modified runtime behaviours at the abstraction level. Our exploratory study shows that majority of the studied plausible patches (92/96) expose different modifications of runtime behaviours (i.e., captured by the invariant generation tool), compared to correct patches.