Reuse (or Lack Thereof) in Travis CI Specifications: An Empirical Study of CI Phases and Commands

摘要

Continuous Integration (CI) is a widely used practice where code changes are automatically built and tested to check for regression as they appear in the Version Control System (VCS). CI services allow users to customize phases, which define the sequential steps of build jobs that are triggered by changes to the project. While past work has made important observations about the adoption and usage of CI, little is known about patterns of reuse in CI specifications. Should reuse be common in CI specifications, we envision that a tool could guide developers through the generation of CI specifications by offering suggestions based on popular sequences of phases and commands. To assess the feasibility of such a tool, we perform an empirical analysis of the use of different phases and commands in a curated sample of 913 CI specifications for Java-based projects that use Travis CI—one of the most popular public CI service providers. First, we observe that five of nine phases are used in 18%-75% of the projects. Second, for the five most popular phases, we apply association rule mining to discover frequent phase, command, and command category usage patterns. Unfortunately, we observe that the association rules lack sufficient support, confidence, or lift values to be considered statistically significantly interesting. Our findings suggest that the usage of phases and commands in Travis CI specifications are broad and diverse. Hence, we cannot provide suggestions for Java-based projects as we had envisioned.