Validating and Prioritizing Quality Rules for Managing Technical Debt: An Industrial Case Study

One major problem in using static analyzers to manage, monitor, control, and reason about technical debt is that industrial projects have a huge amount of technical debt which reflects hundreds of quality rule violations (e.g., high complex module or low comment density). Moreover the negative impact of violating quality rules (i.e., technical debt interest) may vary across rules or even across contexts. Thus, without a context-specific validation and prioritization of quality rules, developers cannot effectively manage technical debt. This paper reports on a case study aimed at exploring the interest associated with violating quality rules; i.e., we investigate if and which quality rules are important for software developers. Our empirical method consists of a survey and a quantitative analysis of the historical data of a CMMI Level 5 software company. The main result of the quantitative analysis is that classes violating several quality rules are five times more defect prone than classes not violating any rule. The main result of the survey is that some rules are perceived by developers as more important than others; however, there is no false positive (i.e., incorrect rule or null interest). These results pave the way to a better practical use of quality rules to manage technical debt and describe new research directions for building a scientific foundation to the technical debt metaphor.