The Temporality of Technical Debt Introduction on New Code and Confounding Factors

Code Technical Debt (TD) is intentionally or unintentionally created when developers introduce inefficiencies in the codebase. This can be attributed to various reasons such as heavy workload, tight delivery schedule, or developers' lack of experience. Since a software system grows mostly through the addition of new code, it is interesting to study how TD fluctuates along this process. Specifically, in this paper we  investigate: (a) the temporality of code TD introduction in new code, i.e., whether the introduction of TD is stable across the lifespan of the project, or if its evolution presents spikes; and (b) the relation of TD introduction to the development team’s workload in a given period, as well as to the experience of the development team. To answer these questions, we have performed a case study on 47 open source projects from two well-known ecosystems (Apache and Eclipse) as well as additional isolated projects from GitHub (not selected from a specific ecosystem) and inspected the number of TD issues introduced in 6-month sliding temporal windows. The results of the study suggested that: (a) overall, the number of TD issues introduced through new code is a stable measure, although it presents spikes; and (b) the number of commits performed, as well as developers' experience are not strongly correlated to the number of introduced TD issues.