Fix flaky tests in MonitoringSupervisor and AlertNotifier

- Add Mox stub setup in supervisor_test.exs to handle DeviceMonitor ping calls
- Change alert_notifier_test.exs to async: true to prevent mailbox contamination
- All 1066 tests now passing with 0 failures

test/towerops/alerts/alert_notifier_test.exs

@@ -1,5 +1,5 @@
 defmodule Towerops.Alerts.AlertNotifierTest do
-  use Towerops.DataCase, async: false
+  use Towerops.DataCase, async: true
 
   import Swoosh.TestAssertions
   import Towerops.AccountsFixtures

test/towerops/monitoring/supervisor_test.exs

@@ -1,12 +1,19 @@
 defmodule Towerops.Monitoring.SupervisorTest do
   use Towerops.DataCase, async: false
 
+  import Mox
   import Towerops.AccountsFixtures
 
+  alias Towerops.Monitoring.PingMock
   alias Towerops.Monitoring.Supervisor, as: MonitoringSupervisor
   alias Towerops.Snmp.PollerRegistry
 
+  setup :verify_on_exit!
+
   setup do
+    # Stub ping calls for any monitors that start during tests
+    # Allow any number of ping calls (monitors ping on init)
+    stub_with(PingMock, Towerops.Monitoring.PingStub)
     # Start Monitoring.Supervisor for these tests
     start_supervised!(MonitoringSupervisor)