Add tests for creating push subscription. [(#1332)](GoogleCloudPlatfo…

…rm/python-docs-samples#1332)

This is a separate PR from actually adding the sample, which is in GoogleCloudPlatform/python-docs-samples#1331.

samples/snippets/subscriber_test.py

@@ -25,6 +25,7 @@
 PROJECT = os.environ['GCLOUD_PROJECT']
 TOPIC = 'subscription-test-topic'
 SUBSCRIPTION = 'subscription-test-subscription'
+ENDPOINT = 'https://{}.appspot.com/push'.format(PROJECT)
 
 
 @pytest.fixture(scope='module')
@@ -97,6 +98,21 @@ def _():
         assert subscriber_client.get_subscription(subscription_path)
 
 
+def test_create_push(subscriber_client):
+    subscription_path = subscriber_client.subscription_path(
+        PROJECT, SUBSCRIPTION)
+    try:
+        subscriber_client.delete_subscription(subscription_path)
+    except Exception:
+        pass
+
+    subscriber.create_push_subscription(PROJECT, TOPIC, SUBSCRIPTION, ENDPOINT)
+
+    @eventually_consistent.call
+    def _():
+        assert subscriber_client.get_subscription(subscription_path)
+
+
 def test_delete(subscriber_client, subscription):
     subscriber.delete_subscription(PROJECT, SUBSCRIPTION)