'Test that _init_tk_type sets _tk_type according to platform.'

def test_init_sets_tktype(self):

    for (platform, types) in (('darwin', alltypes), ('other', nontypes)):
        with self.subTest(platform=platform):
            macosx.platform = platform
            (macosx._tk_type == None)
            macosx._init_tk_type()
            self.assertIn(macosx._tk_type, types)
