'Test when db object does not have cell_mapping'

def test_from_db_object_no_cell_map(self):

    fake_cell = test_cell_mapping.get_db_mapping(id=1)
    db_mapping = get_db_mapping(mapped_cell=fake_cell)
    db_mapping.pop('cell_mapping')
    fake_cell_obj = objects.CellMapping(self.context, **fake_cell)
    mapping_obj = objects.HostMapping()._from_db_object(self.context, objects.HostMapping(), db_mapping)
    with mock.patch.object(host_mapping.HostMapping, '_get_cell_mapping') as mock_load:
        mock_load.return_value = fake_cell_obj
        self.compare_obj(mapping_obj, db_mapping, subs={'cell_mapping': 'cell_id'}, comparators={'cell_mapping': self._check_cell_map_value})
        mock_load.assert_called_once_with()
