Extending an objc unit test class runs the superclass's tests again

Question

I am writing Objective-C unit tests in Xcode. I would like to extend my base class so I can reuse my setUp/tearDown methods. I created a header and put the imports there, since Xcode defaults to making just an implementation file.

Extending the base class works fine, except that all of its test methods are run a second time (or n times, depending on number of children).

My question is if this is the appropriate practice, or should I try something like base classes with no test methods?