Test for , with warning.

google/cloud/datastore/client.py

@@ -14,6 +14,7 @@
 """Convenience wrapper for invoking APIs/factories w/ a project."""
 
 import os
+import warnings
 
 import google.api_core.client_options
 from google.auth.credentials import AnonymousCredentials
@@ -882,6 +883,11 @@ def reserve_ids(self, complete_key, num_ids, retry=None, timeout=None):
         Please use either :meth:`reserve_ids_multi` (recommended) or
         :meth:`reserve_ids_sequential`.
         """
+        message = (
+            "Client.reserve_ids is deprecated. Please use "
+            "Client.reserve_ids_multi or Client.reserve_ids_sequential",
+        )
+        warnings.warn(message, DeprecationWarning)
         return self.reserve_ids_sequential(
             complete_key, num_ids, retry=retry, timeout=timeout
         )

tests/system/test_system.py

@@ -15,6 +15,7 @@
 import datetime
 import os
 import unittest
+import warnings
 
 import requests
 import six
@@ -109,6 +110,18 @@ def test_reserve_ids_sequential(self):
         num_ids = 10
         Config.CLIENT.reserve_ids_sequential(Config.CLIENT.key("Kind", 1234), num_ids)
 
+    def test_reserve_ids(self):
+        with warnings.catch_warnings(record=True) as warned:
+            num_ids = 10
+            Config.CLIENT.reserve_ids(Config.CLIENT.key("Kind", 1234), num_ids)
+
+        warned = [
+            warning
+            for warning in warned
+            if "reserve_ids_sequential" in str(warning.message)
+        ]
+        assert len(warned) == 1
+
     def test_reserve_ids_multi(self):
         # Smoke test to make sure it doesn't blow up. No return value or
         # verifiable side effect to verify.