diff --git a/src/ZB.MOM.WW.MxGateway.Worker.Tests/Probes/AlarmSubtagLiveSmokeTests.cs b/src/ZB.MOM.WW.MxGateway.Worker.Tests/Probes/AlarmSubtagLiveSmokeTests.cs
index a8b1ad5..342756c 100644
--- a/src/ZB.MOM.WW.MxGateway.Worker.Tests/Probes/AlarmSubtagLiveSmokeTests.cs
+++ b/src/ZB.MOM.WW.MxGateway.Worker.Tests/Probes/AlarmSubtagLiveSmokeTests.cs
@@ -368,6 +368,16 @@ public sealed class AlarmSubtagLiveSmokeTests
             transitions.Enqueue(e);
         };
 
+        // Log every raw subtag/source value-change so we can see the source
+        // attribute's runtime type + value (to drive it with the right type).
+        source.ValueChanged += (_, c) =>
+        {
+            string v = c.Value == null
+                ? "<null>"
+                : string.Format("{0} ({1})", c.Value, c.Value.GetType().Name);
+            Log(string.Format("raw ValueChanged: {0} = {1}", c.ItemAddress, v));
+        };
+
         // Advise the alarm subtags (InAlarm/Acked/Priority/AckMsg).
         consumer.Subscribe(string.Format(@"\\{0}\Galaxy!{1}", Environment.MachineName, Group));
         // Also advise the source attribute so it is an active, writable item