perf(runtime): apply-path cache write off-mailbox; stash deferred dispatches

tests/Server/ZB.MOM.WW.OtOpcUa.Runtime.Tests/Harness/RuntimeActorTestBase.cs

@@ -55,8 +55,30 @@ akka {
     }
 }";
 
+    /// <summary>
+    ///     The same single-node HOCON at a caller-chosen <c>loglevel</c>.
+    /// </summary>
+    /// <remarks>
+    ///     A log event below <c>akka.loglevel</c> is never published to the EventStream at all, so
+    ///     neither <c>EventFilter</c> nor an EventStream-subscribed probe can see it. A test whose
+    ///     subject IS a log line (e.g. "this Debug line must be emitted exactly once, not in a spin")
+    ///     therefore has to raise the level for its own ActorSystem; the default stays
+    ///     <c>WARNING</c> so the other 40-odd classes keep their quiet output.
+    /// </remarks>
+    /// <param name="level">An Akka log level — <c>DEBUG</c>, <c>INFO</c>, <c>WARNING</c>, <c>ERROR</c>.</param>
+    /// <returns>The base test HOCON with its <c>loglevel</c> replaced.</returns>
+    protected static string AkkaTestHoconAtLevel(string level) =>
+        AkkaTestHocon.Replace(@"loglevel = ""WARNING""", $@"loglevel = ""{level}""", StringComparison.Ordinal);
+
     /// <summary>Initializes a new instance of the RuntimeActorTestBase class with Akka test setup.</summary>
-    protected RuntimeActorTestBase() : base(AkkaTestHocon)
+    protected RuntimeActorTestBase() : this(AkkaTestHocon)
+    {
+    }
+
+    /// <summary>Initializes a new instance of the RuntimeActorTestBase class with caller-supplied HOCON.</summary>
+    /// <param name="hocon">The Akka configuration for this class's ActorSystem — usually
+    /// <see cref="AkkaTestHoconAtLevel"/>.</param>
+    protected RuntimeActorTestBase(string hocon) : base(hocon)
     {
         var cluster = Akka.Cluster.Cluster.Get(Sys);
         cluster.Join(cluster.SelfAddress);