Added test to ensure the test harness observes messages published via…

… the bus

tests/MassTransit.Tests/Testing/BusPublish_Specs.cs

@@ -0,0 +1,60 @@
+namespace MassTransit.Tests.Testing
+{
+    using System.Threading.Tasks;
+    using MassTransit.Testing;
+    using Microsoft.Extensions.DependencyInjection;
+    using NUnit.Framework;
+
+
+    [TestFixture]
+    public class BusPublish_Specs
+    {
+        [Test]
+        public async Task Should_observe_published_event()
+        {
+            //Arrange
+            var provider = new ServiceCollection()
+                .AddScoped<IMyApplicationService, MyApplicationService>()
+                .AddMassTransitTestHarness()
+                .BuildServiceProvider(true);
+
+            var harness = provider.GetTestHarness();
+
+            await harness.Start();
+
+            var service = harness.Scope.ServiceProvider.GetRequiredService<IMyApplicationService>();
+
+            await service.Register();
+
+            Assert.That(await harness.Published.Any<MyMessage>());
+        }
+
+
+        public class MyMessage
+        {
+        }
+
+
+        public interface IMyApplicationService
+        {
+            Task Register();
+        }
+
+
+        class MyApplicationService :
+            IMyApplicationService
+        {
+            readonly IBus _bus;
+
+            public MyApplicationService(IBus bus)
+            {
+                _bus = bus;
+            }
+
+            public async Task Register()
+            {
+                await _bus.Publish(new MyMessage());
+            }
+        }
+    }
+}