A Large-Scale Empirical Study on Self-Admitted Technical Debt

Technical debt is a metaphor introduced by Cunningham to indicate "not quite right code which we postpone making it right". Examples of technical debt are code smells and bug hazards. Several techniques have been proposed to detect different types of technical debt. Among those, Potdar and Shihab defined heuristics to detect instances of self-admitted technical debt in code comments, and used them to perform an empirical study on five software systems to investigate the phenomenon. Still, very little is known about the diffusion and evolution of technical debt in software projects.This paper presents a differentiated replication of the work by Potdar and Shihab. We run a study across 159 software projects to investigate the diffusion and evolution of self-admitted technical debt and its relationship with software quality. The study required the mining of over 600K commits and 2 Billion comments as well as a qualitative analysis performed via open coding.Our main findings show that self-admitted technical debt (i) is diffused, with an average of 51 instances per system, (ii) is mostly represented by code (30%), defect, and requirement debt (20% each), (iii) increases over time due to the introduction of new instances that are not fixed by developers, and (iv) even when fixed, it survives long time (over 1,000 commits on average) in the system.