About the name: abstract_tests could be used e.g.:

  @abstract_tests
  class AbcSetTests(TestCase):
      # test abc.Set
      Set = abstract_property()

      def setUp(self):
          self.set = self.Set('abc')

      def test_difference(self):
          self.assert... 
    
      def test_union(self):
          self.assert...

It is clear that AbcSetTests do not run because the class is abstract
(can't create an instance).  It is clear that to create a concrete test,
you need to subclass the abstract class (serve as a base class):

  class BuiltinSetTests(AbcSetTests):
      # test builtins.set
      Set = set

  class FrozenSetTests(AbcSetTests):
      # test frozenset
      Set = frozenset

It might not be necessary to enforce all abstract constraints in the
implementation initially. The only thing that needs to be implemented is
that tests from @abstract_tests decorated class should not be run.