@PaulWoitaschek right now, with our built in Virtual Device Testing feature you can only run instrumentation tests for a single APK per build.
Feel free to create a #feature-request, or register the apps as separate apps on bitrise.io (you can register the same repo multiple times), or use Firebase TestLab directly via scripts (How-to run Android tests on Firebase TestLab).
If you’d have any questions just let us know! 