Add worker alert and notification tests

worker/app/scheduler.py

@@ -154,7 +154,10 @@ class Scheduler:
                     .order_by(Incident.opened_at.desc())
                     .limit(1)
                 )
-                if latest_incident is not None and latest_incident.opened_at + timedelta(seconds=rule.cooldown_seconds) > now:
+                if (
+                    latest_incident is not None
+                    and self._as_utc(latest_incident.opened_at) + timedelta(seconds=rule.cooldown_seconds) > now
+                ):
                     return
 
             incident = Incident(
@@ -221,6 +224,12 @@ class Scheduler:
             response = await client.post(url, json={"username": username, "text": message})
             response.raise_for_status()
 
+    @staticmethod
+    def _as_utc(value: datetime) -> datetime:
+        if value.tzinfo is None:
+            return value.replace(tzinfo=UTC)
+        return value.astimezone(UTC)
+
     def _format_incident_message(self, incident: Incident, monitor: Monitor, event_type: str) -> str:
         if event_type == "resolved":
             title = f"RESOLVED: {monitor.name} recovered"