Studying Fine-Grained Co-evolution Patterns of Production and Test Code

Numerous software development practices suggest updating the test code whenever the production code is changed. However, previous studies have shown that co-evolving test and production code is generally a difficult task that needs to be thoroughly investigated. In this paper we perform a study that, following a mixed methods approach, investigates fine-grained co-evolution patterns of production and test code. First, we mine fine-grained changes from the evolution of 5 open-source systems. Then, we use an association rule mining algorithm to generate the co-evolution patterns. Finally, we interpret the obtained patterns by performing a qualitative analysis. The results show 6 co-evolution patterns and provide insights into their appearance along the history of the analyzed software systems. Besides providing a better understanding of how test code evolves, these findings also help identify gaps in the test code thereby assisting both researchers and developers.