Stop calling fixures as functions in the tests

tests/app/invite/test_invite_rest.py

@@ -3,6 +3,7 @@ import pytest
 
 from app.models import Notification, SMS_AUTH_TYPE, EMAIL_AUTH_TYPE
 from tests import create_authorization_header
+from tests.app.db import create_invited_user
 
 
 @pytest.mark.parametrize('extra_args, expected_start_of_invite_url', [
@@ -118,16 +119,11 @@ def test_create_invited_user_invalid_email(client, sample_service, mocker, fake_
 
 
 def test_get_all_invited_users_by_service(client, notify_db, notify_db_session, sample_service):
-
-    from tests.app.conftest import sample_invited_user
     invites = []
     for i in range(0, 5):
         email = 'invited_user_{}@service.gov.uk'.format(i)
+        invited_user = create_invited_user(sample_service, to_email_address=email)
 
-        invited_user = sample_invited_user(notify_db,
-                                           notify_db_session,
-                                           sample_service,
-                                           email)
         invites.append(invited_user)
 
     url = '/service/{}/invite'.format(sample_service.id)