I need to use unittest in python to write some tests. I am testing the behavior of 2 classes, A and B, that have a lot of overlap in behavior because they are both subclasses of C, which is abstract. I would really like to be able to write 3 testing classes: ATestCase, BTestCase, and AbstractTestCase, where AbstractTestCase defines the common setup logic for ATestCase and BTestCase, but does not itself run any tests. ATestCase and BTestCase would be subclasses of AbstractTestCase and would define behavior/input data specific to A and B. 
Is there a way to create an abstract class via python unittest that can take care of setup functionality by inheriting from TestCase, but not actually run any tests?
I tried Łukasz’s answer and it works, but I don’t like OK (SKIP=<number>) messages.  For my own desires and aims for having a test suite I don’t want me or someone to start trusting any particular number of skipped tests, or not trusting and digging into the test suite and asking why something was skipped, and always?, and on purpose?  For me that’s a non-starter.
I happen to use nosetests exclusively, and by convention test classes starting with _ are not run, so naming my base class _TestBaseClass is sufficient.
I tried this in Pycharm with Unittests and py.test and both of those tried to run my base class  and its tests resulting in errors because there’s no instance data in the abstract base class. Maybe someone with specific knowledge of either of those runners could make a suite, or something, that bypasses the base class.
python unittest inheritance - abstract test class