test: unit tests for send_step_failure_notification AttributeError regression

Verifies that the module-level _check_cascading_vars is called correctly
(not as self._check_cascading_vars) and that a notification is queued
when step failure occurs.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

changedetectionio/notification_service.py

@@ -496,7 +496,7 @@ Thanks - Your omniscient changedetection.io installation.
         n_object = NotificationContextData({
             'notification_title': f"Changedetection.io - Alert - Browser step at position {step} could not be run",
             'notification_body': body,
-            'notification_format': self._check_cascading_vars('notification_format', watch),
+            'notification_format': _check_cascading_vars(self.datastore, 'notification_format', watch),
         })
         n_object['markup_text_links_to_html_links'] = n_object.get('notification_format').startswith('html')
 

changedetectionio/tests/unit/test_step_failure_notification.py

@@ -0,0 +1,68 @@
+"""
+Unit test for send_step_failure_notification regression.
+
+Before the fix, line 499 called self._check_cascading_vars('notification_format', watch)
+which raises AttributeError because _check_cascading_vars is a module-level function,
+not a method of NotificationService.
+"""
+
+import queue
+from unittest.mock import MagicMock
+
+
+def _make_datastore(watch_uuid, notification_url):
+    """Minimal datastore mock that NotificationService and _check_cascading_vars need."""
+    watch = MagicMock()
+    watch.get = lambda key, default=None: {
+        'uuid': watch_uuid,
+        'url': 'https://example.com',
+        'notification_urls': [notification_url],
+        'notification_format': '',
+        'notification_muted': False,
+    }.get(key, default)
+    watch.__getitem__ = lambda self, key: watch.get(key)
+
+    datastore = MagicMock()
+    datastore.data = {
+        'watching': {watch_uuid: watch},
+        'settings': {
+            'application': {
+                'notification_urls': [],
+                'notification_format': 'text',
+                'filter_failure_notification_threshold_attempts': 3,
+            }
+        }
+    }
+    datastore.get_all_tags_for_watch.return_value = {}
+    return datastore, watch
+
+
+def test_send_step_failure_notification_does_not_raise():
+    """send_step_failure_notification must not raise AttributeError (wrong self. prefix on module-level function)."""
+    from changedetectionio.notification_service import NotificationService
+
+    watch_uuid = 'test-uuid-1234'
+    notification_q = queue.Queue()
+    datastore, _ = _make_datastore(watch_uuid, 'post://localhost/test')
+    service = NotificationService(datastore=datastore, notification_q=notification_q)
+
+    # Before the fix this raised:
+    # AttributeError: 'NotificationService' object has no attribute '_check_cascading_vars'
+    service.send_step_failure_notification(watch_uuid=watch_uuid, step_n=0)
+
+
+def test_send_step_failure_notification_queues_item():
+    """A notification object should be placed on the queue when URLs are configured."""
+    from changedetectionio.notification_service import NotificationService
+
+    watch_uuid = 'test-uuid-5678'
+    notification_q = queue.Queue()
+    datastore, _ = _make_datastore(watch_uuid, 'post://localhost/test')
+    service = NotificationService(datastore=datastore, notification_q=notification_q)
+
+    service.send_step_failure_notification(watch_uuid=watch_uuid, step_n=1)
+
+    assert not notification_q.empty(), "Expected a notification to be queued"
+    item = notification_q.get_nowait()
+    assert 'notification_title' in item
+    assert 'position 2' in item['notification_title']