[en] Many software development projects frequently rely on testing-related libraries to test the functionality of the software product automatically and efficiently. To obtain insights in the nature of the evolution of testing library usage, we empirically analyzed the usage of eight testing-related libraries in 6,424 open source Java projects hosted on GitHub. We observed how frequently specific (pairs of) versions of libraries are used over time, for how much they are used within a project and we identified the delay to upgrade to a new version. We also identified over time the most used packages of libraries and we analyzed if groups of packages are usually used together. We studied the evolution of the number of test Java files and we also studied how often developers use testing libraries to test classes that provide a particular functionality. We found that some versions of certain libraries are quickly adopted than the others and some of them are quickly upgraded. We observed that most packages of some libraries tend to be used in a few numbers of Java files. These findings may pave the way for recommendation tools that allow project developers to choose the most appropriate library and library developers to better maintain their library.
