Problems and Solutions in Applying Continuous Integration and Delivery to 20 Open-Source Cyber-Physical Systems

Continuous integration and delivery (CI/CD) have been shown to be very useful to improve the quality of software products (e.g., increasing their reliability or maintainability), and their development processes, e.g., by shortening release cycles. Applying CI/CD in the context of Cyber-Physical Systems (CPSs) can be particularly important, given that many of those systems can have safety-critical properties, and given their interaction with hardware or simulators during the development phase. This paper empirically analyzes how CI/CD is enacted in CPSs when considering the context of open-source projects, that often (also) rely on hosted CI/CD so-lutions, and benefit of an open-source development community. We qualitatively analyze a statistically significant sample of 670 pull requests from 20 open-source CPSs hosted on GitHub, to identify and categorize-also keeping into account catalogs from previous literature-bad practices, challenges, mitigation, and restructuring actions. The study reports and discusses the relationships we found between bad practices/challenges and CI/CD restructuring/mitigation strategies, reporting concrete examples, especially those emerging from the intrinsic complexity of CPSs.