Which is the best approach to isolate tests on universal iOS apps?

I'm working on an universal iOS project and my goal is to add as many useful tests that I can. I'm stuck in a point where I have a different behavior between the iPhone and iPad versions and I would like that some tests run only on a specific version. For instance, since the iPhone screen is much smaller than the iPad some buttons will be replaced by an ActionSheet. That said, I would like to know which is the best way to isolate those tests.

My first idea was to create a specific test target for each device, however I think this solution would make it harder to understand what is being tested in general. My current solution for this is to check the device, on each test case, before running the test and skip it if necessary.