add test for notification status return value

to ensure we never break compatibility

tests/app/notifications/test_rest.py

@@ -618,6 +618,44 @@ def test_get_notifications_for_service_returns_merged_template_content(notify_ap
             }
 
 
+def test_get_notification_public_api_format_is_not_changed(notify_api, sample_notification):
+    with notify_api.test_request_context(), notify_api.test_client() as client:
+        auth_header = create_authorization_header(service_id=sample_notification.service_id)
+
+        response = client.get(
+            '/notifications/{}'.format(sample_notification.id),
+            headers=[auth_header])
+
+        assert response.status_code == 200
+        notification = json.loads(response.get_data(as_text=True))['data']['notification']
+        # you should never remove things from this list!
+        assert set(notification.keys()) == {
+            # straight from db
+            'id',
+            'to',
+            'job_row_number',
+            'template_version',
+            'billable_units',
+            'notification_type',
+            'created_at',
+            'sent_at',
+            'sent_by',
+            'updated_at',
+            'status',
+            'reference',
+
+            # relationships
+            'template',
+            'service',
+            'job',
+            'api_key',
+
+            # other
+            'body',
+            'content_char_count'
+        }
+
+
 @pytest.mark.xfail(strict=True, raises=NeededByTemplateError)
 def test_get_notification_selects_correct_template_for_personalisation(notify_api,
                                                                        notify_db,