Defect Density Measurements Using COSMIC - Experiences with Mobile Apps and Embedded Systems

Defect Density Measurements based on functional size have big advantages over traditional approaches based on counting entries in defect repositories. Using structural information, defects can be located within data movements using the ISO/IEC 19761 COSMIC framework. Consequently, defect counts and defect density indicators become comparable among different projects and products, and can even be used for contracting purposes and in acceptance criteria. This article explores modern defect density measurements in two different areas: first, in mobile apps, where functionality spreads between server and devices and defects might arise at communication interfaces between server and devices, and second, in instruments with embedded software ("Internet of Things"), where defects occur when interfacing between different functional users. This yields new insights into origin of defects, and, consequently, leads to defect avoidance strategies. Also, it is shown how ISO/IEC 20926 IFPUG can be used to identify layered application boundaries within the counting scope, establishing effective test scenarios useful for counting defects with ISO/IEC 19761 COSMIC. A best practice for setting application boundaries is proposed that applies both to IFPUG and COSMIC.