Ensure notifications have billable units and provider if sending fails

If we try to send an SMS to the provider and the provider throws an exception
(because they return a 503 status code) the notification should retry. But if
we get the callback from the provider before the notification has been retried, the
notification will have no billable units or provider set.

To avoid this, we now set billable_units and provider even if there has been
an exception from our provider.

tests/app/celery/test_provider_tasks.py

@@ -117,6 +117,7 @@ def test_send_sms_should_switch_providers_on_provider_failure(sample_notificatio
     provider_to_use.return_value.send_sms.side_effect = Exception('Error')
     switch_provider_mock = mocker.patch('app.delivery.send_to_providers.dao_toggle_sms_provider')
     mocker.patch('app.celery.provider_tasks.deliver_sms.retry')
+    mocker.patch('app.delivery.send_to_providers.update_notification_provider')
 
     deliver_sms(sample_notification.id)
 

tests/app/delivery/test_send_to_providers.py

@@ -562,6 +562,25 @@ def test_should_update_billable_units_according_to_research_mode_and_key_type(
     assert sample_notification.billable_units == billable_units
 
 
+def test_should_set_notification_billable_units_and_provider_if_sending_to_provider_fails(
+    notify_db,
+    sample_service,
+    sample_notification,
+    mocker,
+):
+    mocker.patch('app.mmg_client.send_sms', side_effect=Exception())
+    mocker.patch('app.delivery.send_to_providers.dao_toggle_sms_provider')
+
+    sample_notification.billable_units = 0
+    assert sample_notification.sent_by is None
+
+    with pytest.raises(Exception):
+        send_to_providers.send_sms_to_provider(sample_notification)
+
+    assert sample_notification.billable_units == 1
+    assert sample_notification.sent_by == 'mmg'
+
+
 def test_should_send_sms_to_international_providers(
     restore_provider_details,
     sample_sms_template_with_html,