def test_add_identifier(self, mock_identifier):
testWork = Work()
mock_id = MagicMock()
mock_id.value = 'id1'
mock_identifier.returnOrInsert.return_value = mock_id
testID = testWork.addIdentifier('id1')
self.assertEqual(testID.value, 'id1')
def test_add_identifier_err(self, mock_identifier):
testWork = Work()
mock_identifier.returnOrInsert.side_effect = DataError('test error')
testID = testWork.addIdentifier('id1')
self.assertEqual(testID, None)
