Co-evolution of logical couplings and commits for defect estimation

Logical couplings between files in the commit history of a software repository are instances of files being changed together. The evolution of couplings over commits´ history has been used for the localization and prediction of software defects in software reliability. Couplings have been represented in class graphs and change histories on the class-level have been used to identify defective modules. Our new approach inverts this perspective and constructs graphs of ordered commits coupled by common changed classes. These graphs, thus, represent the co-evolution of commits, structured by the change patterns among classes. We believe that co-evolutionary graphs are a promising new instrument for detecting defective software structures. As a first result, we have been able to correlate the history of logical couplings to the history of defects for every commit in the graph and to identify sub-structures of bug-fixing commits over sub-structures of normal commits.