'Volume extend fails when new size would shrink the volume.'

def test_extend_lun_new_size_is_too_small(self):

    new_volume_size = 0
    change_in_size_mb = ((new_volume_size - VOLUME['size']) * units.Ki)
    response = {'success': False, 'msg': 'Invalid    size.    Error:    0x0902000c'}
    failure = exception.ViolinBackendErr
    conf = {'lun.resize_lun.return_value': response}
    self.driver.vmem_mg = self.setup_mock_concerto(m_conf=conf)
    self.driver._send_cmd = mock.Mock(side_effect=failure(message='fail'))
    self.assertRaises(failure, self.driver._extend_lun, VOLUME, change_in_size_mb)
