[WIP] use correct dao function for adding user to service.

Check for no user returned from user dao and return correct
error message.

app/service/rest.py

@@ -19,8 +19,10 @@ from app.dao.services_dao import (
     dao_fetch_all_services,
     dao_create_service,
     dao_update_service,
-    dao_fetch_all_services_by_user
+    dao_fetch_all_services_by_user,
+    dao_add_user_to_service
 )
+
 from app.dao.users_dao import get_model_users
 from app.models import ApiKey
 from app.schemas import (
@@ -162,12 +164,15 @@ def add_user_to_service(service_id, user_id):
         return _service_not_found(service_id)
     user = get_model_users(user_id=user_id)
 
+    if not user:
+        return jsonify(result='error',
+                       message='User not found for id: {}'.format(user_id)), 400
+
     if user in service.users:
         return jsonify(result='error',
                        message='User id: {} already part of service id: {}'.format(user_id, service_id)), 400
 
-    service.users.append(user)
-    dao_update_service(service)
+    dao_add_user_to_service(service, user)
 
     data, errors = service_schema.dump(service)
     return jsonify(data=data), 201

tests/app/service/test_rest.py

@@ -575,6 +575,30 @@ def test_add_existing_user_of_service_to_service_returns400(notify_api, notify_d
             assert result['message'] == expected_message
 
 
+def test_add_unknown_user_to_service_returns400(notify_api, notify_db, notify_db_session, sample_service):
+    with notify_api.test_request_context():
+        with notify_api.test_client() as client:
+
+            incorrect_id = 9876
+
+            auth_header = create_authorization_header(
+                path='/service/{}/users/{}'.format(sample_service.id, incorrect_id),
+                method='POST'
+            )
+
+            resp = client.post(
+                '/service/{}/users/{}'.format(sample_service.id, incorrect_id),
+                headers=[('Content-Type', 'application/json'), auth_header]
+            )
+
+            result = json.loads(resp.get_data(as_text=True))
+            expected_message = 'User not found for id: {}'.format(incorrect_id)
+
+            assert resp.status_code == 400
+            assert result['result'] == 'error'
+            assert result['message'] == expected_message
+
+
 def _user_email_in_list(user_list, email_address):
     for user in user_list:
         if user['email_address'] == email_address: