Instrumentation testing of a private Android library project

I am writing an android library project and want to add unit tests and instrumentation tests to it.

I am having trouble understanding how this might be possible. I first checked out this page and tried implementing what the second bullet point describes. The problem that I ran into was that the library under test only has a few public methods, the rest are package private. So when I tried adding an application module to my project the application module was unable to get a reference to the package-private classes which are what I'm actually trying to test.

The first bullet point from the link is too vague and I don't understand what it's instructing me to do.

Does anyone have experience running unit tests / instrumentation tests on an android library project with package-private classes that need to be tested? If so, could you help me understand the setup that I need for testing that?