Service name uniqueness handled in all cases and tests passing.

tests/conftest.py

@@ -1,5 +1,6 @@
 import uuid
 from datetime import date, datetime, timedelta
+from unittest.mock import Mock
 import pytest
 
 from app import create_app
@@ -18,6 +19,8 @@ from app.notify_client.models import (
     InvitedUser
 )
 
+from notifications_python_client.errors import HTTPError
+
 
 @pytest.fixture(scope='session')
 def app_(request):
@@ -90,6 +93,24 @@ def mock_update_service(mocker):
         'app.notifications_api_client.update_service', side_effect=_update)
 
 
+@pytest.fixture(scope='function')
+def mock_update_service_raise_httperror_duplicate_name(mocker):
+
+    def _update(service_id,
+                service_name,
+                active,
+                limit,
+                restricted,
+                users):
+        json_mock = Mock(return_value={'message': {'name': ["Duplicate service name '{}'".format(service_name)]}})
+        resp_mock = Mock(status_code=400, json=json_mock)
+        http_error = HTTPError(response=resp_mock, message="Default message")
+        raise http_error
+
+    return mocker.patch(
+        'app.notifications_api_client.update_service', side_effect=_update)
+
+
 SERVICE_ONE_ID = "596364a0-858e-42c8-9062-a8fe822260eb"
 SERVICE_TWO_ID = "147ad62a-2951-4fa1-9ca0-093cd1a52c52"