BigQuery user creds sample: add tests.

Mocks out user credentials using the Application Default Credentials,
but uses the same scopes.

Author: tswast

bigquery/cloud-client/client_secrets.json

@@ -24,8 +24,8 @@
 import time
 import uuid
 
-from google_auth_oauthlib import flow
 from google.cloud import bigquery
+from google_auth_oauthlib import flow
 
 
 def wait_for_job(job):
@@ -62,10 +62,10 @@ def run_query(credentials, project, query):
             break
 
 
-def auth_query(project, query, launch_browser=True):
+def authenticate_and_query(project, query, launch_browser=True):
     appflow = flow.InstalledAppFlow.from_client_secrets_file(
-            'client_secrets.json',
-            scopes=['https://www.googleapis.com/auth/bigquery'])
+        'client_secrets.json',
+        scopes=['https://www.googleapis.com/auth/bigquery'])
 
     if launch_browser:
         appflow.run_local_server()
@@ -88,5 +88,5 @@ def auth_query(project, query, launch_browser=True):
 
     args = parser.parse_args()
 
-    auth_query(args.project, args.query, launch_browser=args.launch_browser)
-
+    authenticate_and_query(
+        args.project, args.query, launch_browser=args.launch_browser)

bigquery/cloud-client/user_credentials.py

@@ -0,0 +1,41 @@
+# Copyright 2017 Google Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import os
+
+import google.auth
+import mock
+import pytest
+
+from user_credentials import authenticate_and_query
+
+
+PROJECT = os.environ['GCLOUD_PROJECT']
+
+
+@pytest.fixture
+def mock_flow():
+    flow_patch = mock.patch(
+        'google_auth_oauthlib.flow.InstalledAppFlow', autospec=True)
+
+    with flow_patch as flow_mock:
+        flow_mock.from_client_secrets_file.return_value = flow_mock
+        flow_mock.credentials = google.auth.default()[0]
+        yield flow_mock
+
+
+def test_auth_query_console(mock_flow, capsys):
+    authenticate_and_query(PROJECT, 'SELECT 1+1;', launch_browser=False)
+    out, _ = capsys.readouterr()
+    assert '2' in out