'Ensure that driver.retype() is there.'

def test_retype_is_there(self):

    drv = nfs.NfsDriver(configuration=self.configuration)
    v1 = fake_volume.fake_volume_obj(self.context)
    ret = drv.retype(self.context, v1, mock.sentinel.new_type, mock.sentinel.diff, mock.sentinel.host)
    self.assertEqual((False, None), ret)
