PersistentFSM Test Question

PersistentFSMTest.cs

using System;
using System.Collections.Immutable;

using Akka.Actor;
using Akka.Persistence;
using Akka.Persistence.Fsm;
using Akka.TestKit.NUnit;

using NUnit.Framework;

namespace PersistentTest.Tests
{
    public enum TestActorState
    {
        Counting,
        FinishedCounting
    }

    public class TestActorData
    {
        public int TotalCount { get; set; }
    }

    public class CountedEvent {
        public int Total { get; set; }

        public CountedEvent(int total)
        {
            Total = total;
        }

        public override string ToString()
        {
            return $"{nameof(CountedEvent)} - Total: {Total}";
        }
    }

    public class CountedTooOftenEvent
    {
        public override string ToString()
        {
            return $"{nameof(CountedTooOftenEvent)}";
        }
    }

    public class CountCommand
    {
        public override string ToString()
        {
            return $"{nameof(CountCommand)}";
        }
    }

    public class TestCountingActor : PersistentFSM<TestActorState, TestActorData, object>
    {
        public override string PersistenceId => "testActorId";

        public TestCountingActor()
        {
            StartWith(TestActorState.Counting, new TestActorData());

            When(TestActorState.Counting,
                (e, state) =>
                {
                    Console.WriteLine($"Handling {e.FsmEvent}");
                    
                    if (e.FsmEvent is CountCommand)
                    {
                        Console.WriteLine($"Counting from {e.StateData.TotalCount}");

                        if (e.StateData.TotalCount > 2)
                        {
                            return GoTo(TestActorState.FinishedCounting);
                        }

                        return Stay()
                            .Applying(new CountedEvent(e.StateData.TotalCount + 1));
                    }

                    return state;
                });

            When(TestActorState.FinishedCounting,
                (e, state) =>
                {
                    Console.WriteLine($"Sorry, stopped counting!");

                    return Stop().Applying(new CountedTooOftenEvent());
                });
        }

        protected override TestActorData ApplyEvent(object e, TestActorData data)
        {
            if (e.GetType() == typeof(CountedEvent))
            {
                Console.WriteLine($"Counted {e}");

                return new TestActorData { TotalCount = ((CountedEvent)e).Total };
            }

            return data;
        }

        protected override void OnRecoveryCompleted() { }
    }

    public class TestScenario : TestKit
    {
        private const int ActorInstanceId = 1;

        public TestScenario() : base("akka.suppress-json-serializer-warning = true")
        {

        }

        [Test]
        public void Then_It_Should_Work()
        {
            var testActor = ActorOfAsTestActorRef<TestCountingActor>(Props.Create<TestCountingActor>(), "MyTestActor");

            Watch(testActor);

            var journal = Persistence.Instance.Apply(Sys as ExtendedActorSystem).JournalFor(null);

            journal.Tell(new WriteMessages(new[]
                                               {
                                                   new Akka.Persistence.AtomicWrite(ImmutableList.Create<IPersistentRepresentation>(
                                                       new Persistent(new CountedEvent(1), 1, "testActorId"),
                                                       new Persistent(new CountedEvent(2), 2, "testActorId"),
                                                       new Persistent(new CountedEvent(3), 3, "testActorId"),
                                                       new Persistent(new PersistentFSMBase<TestActorState, TestActorData, object>.StateChangeEvent(TestActorState.FinishedCounting, null), 4, "testActorId")
                                                   ))
                                               }, testActor, ActorInstanceId));

            Console.WriteLine($"Done telling journal");

            testActor.Tell(new CountCommand());

            ExpectTerminated(testActor);
        }
    }
    
    /*
    
    Failed: Timeout 00:00:03 while waiting for a message of type Akka.Actor.Terminated Terminated akka://test/user/MyTestActor. 
   at NUnit.Framework.Assert.Fail(String message, Object[] args)
   at Akka.TestKit.TestKitBase.InternalExpectMsgEnvelope[T](Nullable`1 timeout, Action`2 assert, String hint, Boolean shouldLog)
   at Akka.TestKit.TestKitBase.InternalExpectMsgEnvelope[T](Nullable`1 timeout, Action`1 msgAssert, Action`1 senderAssert, String hint)
   at Akka.TestKit.TestKitBase.InternalExpectMsg[T](Nullable`1 timeout, Action`1 msgAssert, String hint)
   at Akka.TestKit.TestKitBase.ExpectTerminated(IActorRef target, Nullable`1 timeout, String hint)
   at PersistentTest.Tests.TestScenario.Then_It_Should_Work() in d:\GG.Service.IssuerLookup\PersistentTest\PersistentTest.Tests\Class1.cs:line 139

Done telling journal
Counted CountedEvent - Total: 1
Counted CountedEvent - Total: 2
Counted CountedEvent - Total: 3
Handling CountCommand
Counting from 3
Counted CountedEvent - Total: 1
[ERROR][06/06/2016 15:57:35][Thread 0004][akka://test/user/MyTestActor] Object reference not set to an instance of an object.
Cause: System.NullReferenceException: Object reference not set to an instance of an object.
   at Akka.Persistence.Eventsourced.PeekApplyHandler(Object payload)
   at Akka.Persistence.Eventsourced.CommonProcessingStateBehavior(Object message, Action`1 onWriteMessageComplete)
   at Akka.Persistence.Eventsourced.<ProcessingCommands>b__90_0(Receive receive, Object message)
   at Akka.Persistence.Eventsourced.AroundReceive(Receive receive, Object message)
   at Akka.Actor.ActorCell.ReceiveMessage(Object message)
   at Akka.Actor.ActorCell.Invoke(Envelope envelope)
Counted CountedEvent - Total: 1
Counted CountedEvent - Total: 2
Counted CountedEvent - Total: 3
[WARNING][06/06/2016 15:57:38][Thread 0016][akka://test/user/testActor1] DeadLetter from [akka://test/user/testActor1] to [akka://test/user/testActor1]: <Received dead system message: <DeathWatchNotification>: TestActor[akka://test/user/MyTestActor], ExistenceConfirmed=True, AddressTerminated=False>
[WARNING][06/06/2016 15:57:38][Thread 0016][akka://test/user] DeadLetter from [akka://test/user] to [akka://test/user]: <Received dead system message: <DeathWatchNotification>: [akka://test/user/testActor1], ExistenceConfirmed=True, AddressTerminated=False>
[WARNING][06/06/2016 15:57:38][Thread 0016][akka://test/user] DeadLetter from [akka://test/user] to [akka://test/user]: <Received dead system message: <DeathWatchNotification>: TestActor[akka://test/user/MyTestActor], ExistenceConfirmed=True, AddressTerminated=False>
[WARNING][06/06/2016 15:57:38][Thread 0016][akka://test/user] DeadLetter from [akka://test/user] to [akka://test/user]: <Received dead system message: <DeathWatchNotification>: [akka://test/user/$b], ExistenceConfirmed=True, AddressTerminated=False>
[INFO][06/06/2016 15:57:38][Thread 0015][akka://test/user/testActor1] Message DeathWatchNotification from akka://test/user/testActor1 to akka://test/user/testActor1 was not delivered. 1 dead letters encountered.
[INFO][06/06/2016 15:57:38][Thread 0015][akka://test/user] Message DeathWatchNotification from akka://test/user to akka://test/user was not delivered. 2 dead letters encountered.
[INFO][06/06/2016 15:57:38][Thread 0015][akka://test/user] Message DeathWatchNotification from akka://test/user to akka://test/user was not delivered. 3 dead letters encountered.
[INFO][06/06/2016 15:57:38][Thread 0015][akka://test/user] Message DeathWatchNotification from akka://test/user to akka://test/user was not delivered. 4 dead letters encountered.
DeadLetter from [akka://test/system] to [akka://test/system]: <<DeathWatchNotification>: [akka://test/system/EventStreamUnsubscriber-1], ExistenceConfirmed=True, AddressTerminated=False>
    
    
    */
}