Removed an update statement to notifications.

It's a small change, but we should remove any db operations that are not necessary.

tests/app/notifications/test_process_letter_notifications.py

@@ -40,3 +40,18 @@ def test_create_letter_notification_sets_reference(sample_letter_template, sampl
     notification = create_letter_notification(data, sample_letter_template, sample_api_key, NOTIFICATION_CREATED)
 
     assert notification.client_reference == 'foo'
+
+
+def test_create_letter_notification_sets_billable_units(sample_letter_template, sample_api_key):
+    data = {
+        'personalisation': {
+            'address_line_1': 'The Queen',
+            'address_line_2': 'Buckingham Palace',
+            'postcode': 'SW1 1AA',
+        },
+    }
+
+    notification = create_letter_notification(data, sample_letter_template, sample_api_key, NOTIFICATION_CREATED,
+                                              billable_units=3)
+
+    assert notification.billable_units == 3

tests/app/notifications/test_process_notification.py

@@ -500,3 +500,22 @@ def test_persist_notification_increments_and_expires_redis_template_usage(
         'service-{}-template-usage-{}'.format(str(sample_template.service_id), day_in_key),
         current_app.config['EXPIRE_CACHE_EIGHT_DAYS']
     )
+
+
+def test_persist_notification_with_billable_units_stores_correct_info(
+    sample_template,
+):
+    persist_notification(
+        template_id=sample_template.id,
+        template_version=sample_template.version,
+        recipient="123 Main Street",
+        service=sample_template.service,
+        personalisation=None,
+        notification_type='letter',
+        api_key_id=None,
+        key_type="normal",
+        billable_units=3
+    )
+    persisted_notification = Notification.query.all()[0]
+
+    assert persisted_notification.billable_units == 3