Added repro for akkadotnet#458

src/Akka.Hosting.TestKit.Tests/Bugfix458Spec.cs

@@ -0,0 +1,50 @@
+using System;
+using System.Threading.Tasks;
+using Akka.Actor;
+using FluentAssertions;
+using Xunit;
+
+namespace Akka.Hosting.TestKit.Tests;
+
+public class Bugfix458Spec : TestKit
+{
+    private class EchoActor : ReceiveActor
+    {
+        public EchoActor()
+        {
+            ReceiveAny(msg => Sender.Tell(msg));
+        }
+    }
+
+    protected override void ConfigureAkka(AkkaConfigurationBuilder builder, IServiceProvider provider)
+    {
+        builder.WithActors((system, registry, resolver) =>
+        {
+            var echoActor = system.ActorOf<EchoActor>("echo");
+            registry.Register<EchoActor>(echoActor);
+        });
+    }
+
+    [Fact]
+    public void Bugfix458_should_resolve_TestActor_in_SynchronousCode()
+    {
+        var echo = ActorRegistry.Get<EchoActor>();
+        echo.Tell("hello");
+        ExpectMsg("hello");
+    }
+
+    [Theory]
+    [InlineData(1)]
+    [InlineData(2)]
+    [InlineData(3)]
+    [InlineData(4)]
+    [InlineData(5)]
+    [InlineData(6)]
+    [InlineData(7)]
+    public async Task Bugfix458_should_resolve_TestActor_in_AsynchronousCode(int _)
+    {
+        var echo = await ActorRegistry.GetAsync<EchoActor>();
+        echo.Tell("hello");
+        await ExpectMsgAsync("hello");
+    }
+}