def METHOD_NAME(self):
    self.assertEqual(
        commonprefix(
            [self.SEP.join(("foo", "bar", "baz")), "foo/qux", "foo/baz/qux"]
        ),
        "foo/",
    )
    self.assertEqual(
        commonprefix([self.SEP.join(("foo", "bar", "baz")), "foo/qux", "baz/qux"]),
        "",
    )