How to write test cases for Project,Library project in Android studio

Currently I am working on creating test cases for my Android project which used Another Android project as Android Library project. In my Android project I didn't do any business logic I have done all logics in my Android Library project,So I just extends my activity into Android library Project Activity. I have written separate Test classes for each Activity in Android Library.If I run each test class It will pass in test.How can I test the whole Android Library Project? and also Android application project?. If I accessed any Android Library project's test class(AndroidLibraryProject/src/androidTest/java/packageName/testCase.java) in my Android Application Project it showed does not exist error message while run the class.How can I test whole project both Android application project and Library project