The effect of evolutionary coupling on software defects: an industrial case study on a legacy system

Evolutionary coupling is defined as the implicit relationship between two or more software artifacts that are frequently changed together. In this study we investigate the effect of evolutionary coupling on defect proneness of a large financial legacy software in an industrial software development environment. We collected historical data for 5 years from 3 different software repositories containing 150 thousand files on 274 modules. Our results indicate that there is a positive correlation between evolutionary coupling and defect measures. Furthermore, we built linear and logistic regression models by using evolutionary coupling measures in order to explain defects. Although regression analysis results show that evolutionary coupling measures can be useful to explain defects, especially for modules in which high correlation is detected, explanatory power decreases dramatically with the decreasing correlation.