test: verify missing-snapshot ServiceLevel timer behavior

tests/Server/ZB.MOM.WW.OtOpcUa.Runtime.Tests/OpcUa/OpcUaPublishActorFreshnessTests.cs

@@ -1,5 +1,7 @@
 using System.Collections.Concurrent;
 using Akka.Actor;
+using Akka.TestKit;
+using Akka.TestKit.Xunit2;
 using Shouldly;
 using Xunit;
 using ZB.MOM.WW.OtOpcUa.Commons.Messages.Redundancy;
@@ -134,6 +136,82 @@ public sealed class OpcUaPublishActorFreshnessTests : RuntimeActorTestBase
         AwaitAssert(() => publisher.Levels.Last().ShouldBe((byte)110), PresenceBudget);
     }
 
+    [Fact]
+    public void Missing_local_snapshot_entry_retries_zero_on_timer_and_recovers()
+    {
+        var publisher = new RetryZeroPublisher();
+        var clock = new ControlledClock();
+        var local = NodeId.Parse("missing-entry-node");
+        var actor = Sys.ActorOf(OpcUaPublishActor.PropsForTests(
+            serviceLevel: publisher, localNode: local, dbLess: true,
+            healthTickInterval: TimeSpan.FromMilliseconds(25), utcNow: clock.Read));
+        actor.Tell(Snapshot(local, false, clock.Now));
+        AwaitAssert(() => publisher.Levels.ShouldBe(new byte[] { 240 }), PresenceBudget);
+
+        // Only this snapshot Tell requests the first zero. Fail it and the next attempt so
+        // subsequent zero attempts must come from the periodic timer, exercising the null-entry
+        // branch repeatedly rather than mistaking the Detached branch for missing-node coverage.
+        actor.Tell(Snapshot(NodeId.Parse("other-node"), false, clock.Now));
+        AwaitAssert(() => publisher.Levels.ShouldBe(new byte[] { 240, 0 }), PresenceBudget);
+        publisher.ZeroAttempts.ShouldBeGreaterThanOrEqualTo(3);
+
+        actor.Tell(Snapshot(local, false, clock.Now));
+        AwaitAssert(() => publisher.Levels.ShouldBe(new byte[] { 240, 0, 240 }), PresenceBudget);
+        clock.Advance(TimeSpan.FromSeconds(30) + TimeSpan.FromTicks(1));
+        AwaitAssert(() => publisher.Levels.ShouldBe(new byte[] { 240, 0, 240, 200 }), PresenceBudget);
+    }
+
+    [Fact]
+    public void No_snapshot_startup_does_not_publish_across_virtual_timer_periods()
+    {
+        // This actor requires the Cluster extension, but the absent/missing-entry guards do
+        // not inspect membership. Do not self-join: the ordinary harness waits for Up in its
+        // constructor, which cannot progress with a frozen scheduler.
+        using var local = new TestKit(AkkaTestHocon + @"
+            akka.scheduler.implementation = ""Akka.TestKit.TestScheduler, Akka.TestKit""");
+        var scheduler = (TestScheduler)local.Sys.Scheduler;
+        var publisher = new RetryZeroPublisher();
+        var clock = new ControlledClock();
+        var actor = local.ActorOfAsTestActorRef<OpcUaPublishActor>(OpcUaPublishActor.PropsForTests(
+            serviceLevel: publisher, localNode: NodeId.Parse("no-snapshot-node"), dbLess: true,
+            healthTickInterval: TimeSpan.FromSeconds(1), utcNow: clock.Read));
+
+        // TestActorRef uses the calling-thread dispatcher: Advance completes delivery before
+        // these assertions, including the immediate startup tick and three periodic ticks.
+        for (var period = 0; period < 3; period++)
+            scheduler.Advance(TimeSpan.FromSeconds(1));
+        publisher.Levels.ShouldBeEmpty();
+        publisher.ZeroAttempts.ShouldBe(0);
+        clock.Reads.ShouldBe(0);
+
+        // Positive control: the same registered timer must subsequently retry a failed zero.
+        // No whole snapshot at startup means no publication; a received snapshot missing the
+        // local entry means zero. Keep these two policies explicitly distinct.
+        actor.Tell(Snapshot(NodeId.Parse("other-node"), false, clock.Now));
+        publisher.ZeroAttempts.ShouldBe(1);
+        scheduler.Advance(TimeSpan.FromSeconds(1));
+        publisher.ZeroAttempts.ShouldBe(2);
+        publisher.Levels.ShouldBeEmpty();
+        scheduler.Advance(TimeSpan.FromSeconds(1));
+        publisher.ZeroAttempts.ShouldBe(3);
+        publisher.Levels.ShouldBe(new byte[] { 0 });
+        clock.Reads.ShouldBe(0);
+    }
+
+    private sealed class RetryZeroPublisher : IServiceLevelPublisher
+    {
+        private readonly ConcurrentQueue<byte> _levels = new();
+        private int _zeroAttempts;
+        public byte[] Levels => _levels.ToArray();
+        public int ZeroAttempts => Volatile.Read(ref _zeroAttempts);
+        public void Publish(byte serviceLevel)
+        {
+            if (serviceLevel == 0 && Interlocked.Increment(ref _zeroAttempts) <= 2)
+                throw new InvalidOperationException("test zero-publication failure");
+            _levels.Enqueue(serviceLevel);
+        }
+    }
+
     private sealed class ControlledClock
     {
         private long _ticks = new DateTime(2026, 1, 1, 0, 0, 0, DateTimeKind.Utc).Ticks;