Migrate Notifications interface patterns

tests/test_notifications.py

@@ -21,12 +21,14 @@ from govoplan_notifications.backend.db.models import NotificationDeliveryAttempt
 from govoplan_notifications.backend.router import api_get_notification, api_list_notifications, api_notification_summary, api_update_notification
 from govoplan_notifications.backend.schemas import NotificationCreateRequest, NotificationPreferencesUpdateRequest, NotificationUpdateRequest
 from govoplan_notifications.backend.service import (
+    NotificationError,
     create_notification,
     deliver_pending,
     notification_preferences_response,
     notification_response,
     notification_summary,
     update_notification_preferences,
+    update_notification,
 )
 
 
@@ -222,6 +224,37 @@ class NotificationServiceTests(unittest.TestCase):
                 session.commit()
             enqueue.assert_not_called()
 
+    def test_cancellation_is_limited_to_locally_controllable_delivery_states(self) -> None:
+        with self.Session() as session:
+            notification = create_notification(
+                session,
+                tenant_id="tenant-1",
+                payload=self._inbox_payload(recipient_id="user-1", subject="Cancellation boundary"),
+            )
+            notification.status = "sent"
+            session.flush()
+
+            with self.assertRaisesRegex(
+                NotificationError,
+                "cannot be cancelled from status sent",
+            ):
+                update_notification(
+                    session,
+                    tenant_id="tenant-1",
+                    notification_id=notification.id,
+                    payload=NotificationUpdateRequest(status="cancelled"),
+                )
+
+            notification.status = "queued"
+            cancelled = update_notification(
+                session,
+                tenant_id="tenant-1",
+                notification_id=notification.id,
+                payload=NotificationUpdateRequest(status="cancelled"),
+            )
+            self.assertEqual("cancelled", cancelled.status)
+            self.assertIsNotNone(cancelled.cancelled_at)
+
     def test_action_url_accepts_only_application_relative_paths(self) -> None:
         payload = self._inbox_payload(recipient_id="user-1", subject="Safe action")
         safe = payload.model_copy(update={"action_url": "/calendar?event=event-1#details"})