def METHOD_NAME(self):
    with mock.patch("warnings.warn") as warn:
        self._call_units(units_str="kittens")
    self.assertEqual(warn.call_count, 1)
    self.assertEqual(self.cube.units, "")
    self.assertArrayAlmostEqual(
        self.cube.data, np.ones_like(self.cube.data)
    )
    self.assertEqual(self.cube.data.dtype, np.float32)
    self.assertEqual(self.cube.attributes["invalid_units"], "kittens")