Regression Test Selection for Distributed Software Histories

Abstract. Regression test selection analyzes incremental changes to a codebase and chooses to run only those tests whose behavior may be affected by the latest changes in the code. By focusing on a small subset of all the tests, the testing process runs faster and can be more tightly integrated into the development process. Existing techniques for regres-sion test selection consider two versions of the code at a time, effectively assuming a development process where changes to the code occur in a linear sequence. Modern development processes that use distributed version-control sys-tems are more complex. Software version histories are generally mod-eled as directed graphs; in addition to version changes occurring lin-early, multiple versions can be related by other commands, e.g., branch, merge, rebase, cherry-pick, revert, etc. This paper describes a regression test-selection technique for software developed using modern distributed version-control systems. By modeling different branch or merge com-mands directly in our technique, it computes safe test sets that can be substantially smaller than applying previous techniques to a linearization of the software history. We evaluate our technique on software histories of several large open-source projects. The results are encouraging: our technique obtained an average of 10.89 × reduction in the number of tests over an existing tech-nique while still selecting all tests whose behavior may differ.