Using association rules to study the co-evolution of production & test code

Unit tests are generally acknowledged as an important aid to produce high quality code, as they provide quick feedback to developers on the correctness of their code. In order to achieve high quality, well-maintained tests are needed. Ideally, tests co-evolve with the production code to test changes as soon as possible. In this paper, we explore an approach based on association rule mining to determine whether production and test code co-evolve synchronously. Through two case studies, one with an open source and another one with an industrial software system, we show that our association rule mining approach allows one to assess the co-evolution of product and test code in a software project and, moreover, to uncover the distribution of programmer effort over pure coding, pure testing, or a more test-driven-like practice.