Preserve 'unknown' in ft_billing for sms if the provider is not known.

app/celery/reporting_tasks.py

@@ -1,4 +1,3 @@
-import random
 from datetime import datetime, timedelta
 from app.models import (Notification,
                         Rate,
@@ -44,14 +43,14 @@ def create_nightly_billing(day_start=None):
         Notification.template_id,
         Notification.service_id,
         Notification.notification_type,
-        case(
-            [
-                (Notification.notification_type == 'letter', func.coalesce(Notification.sent_by, 'dvla')),
-                (Notification.notification_type == 'sms',
-                 func.coalesce(Notification.sent_by, random.choice(['mmg', 'firetext'])))
-            ],
-            else_='ses'
-        ).label('sent_by'),  # This could be null - this is a bug to be fixed.
+        func.coalesce(Notification.sent_by,
+                      case(
+                          [
+                              (Notification.notification_type == 'letter', 'dvla'),
+                              (Notification.notification_type == 'sms', 'unknown'),
+                              (Notification.notification_type == 'email', 'ses')
+                          ]),
+                      ).label('sent_by'),
         func.coalesce(Notification.rate_multiplier, 1).label('rate_multiplier'),
         func.coalesce(Notification.international, False).label('international'),
         func.sum(Notification.billable_units).label('billable_units'),

tests/app/celery/test_reporting_tasks.py

@@ -261,7 +261,7 @@ def test_create_nightly_billing_null_sent_by_sms(
     assert record.rate == Decimal(1.33)
     assert record.billable_units == 1
     assert record.rate_multiplier == 1
-    assert record.provider in ['mmg', 'firetext']
+    assert record.provider == 'unknown'
 
 
 @freeze_time('2018-01-15T03:30:00')