Adding system test for datastore failed transactions.

system_tests/datastore.py

@@ -19,6 +19,7 @@
 from gcloud import datastore
 from gcloud.datastore import client
 from gcloud.environment_vars import TESTS_DATASET
+from gcloud.exceptions import Conflict
 # This assumes the command is being run via tox hence the
 # repository root is the current directory.
 from system_tests import populate_datastore
@@ -341,3 +342,31 @@ def test_transaction(self):
  retrieved_entity = CLIENT.get(entity.key)
  self.case_entities_to_delete.append(retrieved_entity)
  self.assertEqual(retrieved_entity, entity)
+
+ def test_failure_with_contention(self):
+ contention_key = 'baz'
+ # Fool the Client constructor to avoid creating a new connection.
+ local_client = datastore.Client(dataset_id=CLIENT.dataset_id,
+ http=object())
+ local_client.connection = CLIENT.connection
+
+ # Insert an entity which will be retrieved in a transaction
+ # and updated outside it with a contentious value.
+ key = local_client.key('BreakTxn', 1234)
+ orig_entity = datastore.Entity(key=key)
+ orig_entity['foo'] = u'bar'
+ local_client.put(orig_entity)
+ self.case_entities_to_delete.append(orig_entity)
+
+ with self.assertRaises(Conflict):
+ with local_client.transaction() as txn:
+ entity_in_txn = local_client.get(key)
+
+ # Update the original entity outside the transaction.
+ orig_entity[contention_key] = u'outside'
+ CLIENT.put(orig_entity)
+
+ # Try to update the entity which we already updated outside the
+ # transaction.
+ entity_in_txn[contention_key] = u'inside'
+ txn.put(entity_in_txn)