You would not call test functions by yourself, the system would do. In this specific case you'd use File::Spec anyway.

What is interesting in this case might be how to skip tests. I think the usual SKIP would work inside the test functions, but there might be some way to mark test functions to be skipped conditionally. Pytest uses "decorators" for this.

@pytest.mark.skipif(sys.platform != 'darwin', reason="Mac tests")
def test_func():
   ...
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