As per review commemnts:

- Add the assert to a test - oops.
- Fix typo in error message.

app/dao/service_sms_sender_dao.py

@@ -108,4 +108,4 @@ def _reset_old_default_to_false(old_default):
 def _raise_when_no_default(old_default):
     # check that the update is not updating the only default to false
     if not old_default:
-        raise Exception("You must have at least one letter contact as the default.", 400)
+        raise Exception("You must have at least one SMS sender as the default.", 400)

app/service/rest.py

@@ -23,8 +23,13 @@ from app.dao.service_inbound_api_dao import (
     reset_service_inbound_api,
     get_service_inbound_api
 )
-from app.dao.service_sms_sender_dao import insert_or_update_service_sms_sender, dao_add_sms_sender_for_service, \
-    dao_update_service_sms_sender, dao_get_service_sms_senders_by_id, dao_get_sms_senders_by_service_id
+from app.dao.service_sms_sender_dao import (
+    insert_or_update_service_sms_sender,
+    dao_add_sms_sender_for_service,
+    dao_update_service_sms_sender,
+    dao_get_service_sms_senders_by_id,
+    dao_get_sms_senders_by_service_id
+)
 from app.dao.services_dao import (
     dao_fetch_service_by_id,
     dao_fetch_all_services,
@@ -71,7 +76,10 @@ from app.errors import (
 from app.models import Service, ServiceInboundApi
 from app.schema_validation import validate
 from app.service import statistics
-from app.service.service_inbound_api_schema import service_inbound_api, update_service_inbound_api_schema
+from app.service.service_inbound_api_schema import (
+    service_inbound_api,
+    update_service_inbound_api_schema
+)
 from app.service.service_senders_schema import (
     add_service_email_reply_to_request,
     add_service_letter_contact_block_request,
@@ -638,7 +646,6 @@ def add_service_sms_sender(service_id):
 
 @service_blueprint.route('/<uuid:service_id>/sms-sender/<uuid:sms_sender_id>', methods=['POST'])
 def update_service_sms_sender(service_id, sms_sender_id):
-    dao_fetch_service_by_id(service_id)
     form = validate(request.get_json(), add_service_sms_sender_request)
 
     sms_sender_to_update = dao_get_service_sms_senders_by_id(service_id=service_id,

tests/app/dao/test_service_sms_sender_dao.py

@@ -66,9 +66,9 @@ def test_dao_get_sms_senders_by_service_id(notify_db_session):
     assert len(results) == 2
     for x in results:
         if x.is_default:
-            x.sms_sender = 'first_sms'
+            assert x.sms_sender == 'first_sms'
         else:
-            x == second_sender
+            assert x == second_sender
 
 
 def test_dao_add_sms_sender_for_service(notify_db_session):