Android: Accessing test classes of project A from project B test classes

I have a common library project that could be extended from other lib projects. In my main lib project I have some instrumentation tests and a common class to share code for testing. If I try to use this common class on the tests of the other lib projects, Android Studio does not return any error but gradle does "Cannot find symbol...". Is there any way to share code amongst tests classes of different projects without leaving it on the main source code?

Thanks!