But passing the file name as argument to a py.test invocation selects only the doctest from that file (wtf!?). Instead, you need to call it like this:

$ py.test -k test_module    # to run the tests from test_module.py
$ py.test -k test_func      # to run tests having the function name test_func

This is documented in the section advanced test selection and running modes of the py.test documentation, although I fail to see how this is advanced.