test: add system tests for mTLS testing (#38)

* test: add system tests for mTLS testing

* Update tests/system.py

tests/system.py

@@ -0,0 +1,34 @@
+# -*- coding: utf-8 -*-
+#
+# Copyright 2020 Google LLC
+#
+# 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
+#
+#     https://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 pytest
+
+from google.cloud import bigquery_connection
+
+
+@pytest.fixture(scope="session")
+def project_id():
+    return os.environ["PROJECT_ID"]
+
+
+def test_list_connections(project_id):
+    client = bigquery_connection.ConnectionServiceClient()
+
+    parent = f"projects/{project_id}/locations/US"
+    connections = list(client.list_connections(parent=parent))
+
+    assert len(connections) >= 0