Clarify the unit test

src/contrib/persistence/Akka.Persistence.Sqlite.Tests/CustomObjectSerializerSpec.cs

@@ -58,16 +58,23 @@ public async Task CustomSerializerTest()
         {
             var probe = CreateTestProbe();
 
+            // Sanity check to see that the system should serialize object type using MySerializer
+            var serializer = Sys.Serialization.FindSerializerForType(typeof(Persisted));
+            serializer.Should().BeOfType<MySerializer>();
+
             var actor = Sys.ActorOf(Props.Create(() => new PersistedActor("a")));
-            actor.Tell("a", probe);
-            probe.ExpectMsg("a");
+            actor.Tell(new Persisted("a"), probe);
+            probe.ExpectMsg(new Persisted("a"));
 
+            // Read the database directly, make sure that we're using the correct object type serializer
             var conn = new SqliteConnection("DataSource=AkkaJournal.db");
             conn.Open();
             const string sql = "SELECT ej.serializer_id FROM event_journal ej WHERE ej.persistence_id = 'a'";
             await using var cmd = new SqliteCommand(sql, conn);
             var record = await cmd.ExecuteReaderAsync();
             await record.ReadAsync();
+
+            // In the bug this fails, the serializer id is JSON id instead of MySerializer id
             record[0].Should().Be(9999);
         }
 
@@ -83,6 +90,33 @@ public Task DisposeAsync()
             return Task.CompletedTask;
         }
     }
+
+    internal sealed class Persisted: IEquatable<Persisted>
+    {
+        public Persisted(string payload)
+        {
+            Payload = payload;
+        }
+
+        public string Payload { get; }
+
+        public bool Equals(Persisted other)
+        {
+            if (ReferenceEquals(null, other)) return false;
+            if (ReferenceEquals(this, other)) return true;
+            return Payload == other.Payload;
+        }
+
+        public override bool Equals(object obj)
+        {
+            return ReferenceEquals(this, obj) || obj is Persisted other && Equals(other);
+        }
+
+        public override int GetHashCode()
+        {
+            return (Payload != null ? Payload.GetHashCode() : 0);
+        }
+    }
 
     internal class MySerializer : Serializer
     {