What constitutes debugging? An exploratory study of debugging episodes

When debugging, developers engage in activities such as navigating, editing, testing, and inspecting code. Despite being the building blocks of debugging, little is known about how they constitute debugging. To address this gap, we introduce the concept of a “debugging episode” which encompasses the time from when a developer first investigates a defect until when the defect is fixed or the developer stops. We observed 11 professional developers working on open source projects, coding 89 debugging episodes and 2135 instances of activities that occurred during them. Six activities were identified: navigate, edit, test, inspect, consult resources, and other miscellaneous activities. We found that developers spent the most time editing (41%) and testing (29%) during debugging. When addressing time-consuming defects, developers engaged in more diverse types of debugging activities, spent more time inspecting program state, navigating code, and consulting external resources, and spent less time testing. We found that the activities developers do while debugging were more similar than different than the activities that make up implementation work. Developers spent a similar fraction of their time editing and navigating during debugging and implementation work. However, debugging involved significantly more time inspecting (16%) than implementation work (2%), while implementation work involved more time consulting resources (24%) than debugging (6%). We conducted semi-structured interviews with ten developers to gain insights into the challenges that cause developers in longer debugging episodes to engage with more activities. Our findings offer insight into the debugging process and the challenges that developers confront, offering implications for the design of debugging tools, improved debugging education, and future research.