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

def test_fail_extend_dedup_lun(self):

    vol = VOLUME.copy()
    vol['volume_type_id'] = '1'
    size_in_mb = (vol['size'] * units.Ki)
    self.driver.vmem_mg = self.setup_mock_concerto()
    type(self.driver.vmem_mg.utility).is_external_head = mock.PropertyMock(return_value=False)
    self.driver._get_volume_type_extra_spec = mock.Mock(return_value='True')
    failure = exception.VolumeDriverException
    self.assertRaises(failure, self.driver._extend_lun, vol, size_in_mb)
