diff --git a/test/MediatR.Tests/NotificationPublisherTests.cs b/test/MediatR.Tests/NotificationPublisherTests.cs
index 052d5230..40999052 100644
--- a/test/MediatR.Tests/NotificationPublisherTests.cs
+++ b/test/MediatR.Tests/NotificationPublisherTests.cs
@@ -1,6 +1,82 @@
-namespace MediatR.Tests;
+using System.Diagnostics;
+using System.Threading;
+using System.Threading.Tasks;
+using MediatR.NotificationPublishers;
+using Microsoft.Extensions.DependencyInjection;
+using Shouldly;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace MediatR.Tests;
 
 public class NotificationPublisherTests
 {
-    
+    private readonly ITestOutputHelper _output;
+
+    public NotificationPublisherTests(ITestOutputHelper output) => _output = output;
+
+    public class Notification : INotification
+    {
+    }
+
+    public class FirstHandler : INotificationHandler<Notification>
+    {
+        public async Task Handle(Notification notification, CancellationToken cancellationToken) 
+            => await Task.Delay(500, cancellationToken);
+    }
+    public class SecondHandler : INotificationHandler<Notification>
+    {
+        public async Task Handle(Notification notification, CancellationToken cancellationToken) 
+            => await Task.Delay(250, cancellationToken);
+    }
+
+    [Fact]
+    public async Task Should_handle_sequentially_by_default()
+    {
+        var services = new ServiceCollection();
+        services.AddMediatR(cfg =>
+        {
+            cfg.RegisterServicesFromAssemblyContaining<Notification>();
+        });
+        var serviceProvider = services.BuildServiceProvider();
+
+        var mediator = serviceProvider.GetRequiredService<IMediator>();
+
+        var timer = new Stopwatch();
+        timer.Start();
+
+        await mediator.Publish(new Notification());
+
+        timer.Stop();
+        
+        timer.ElapsedMilliseconds.ShouldBeGreaterThan(750);
+
+        _output.WriteLine(timer.ElapsedMilliseconds.ToString());
+    }
+
+
+    [Fact]
+    public async Task Should_handle_in_parallel_with_when_all()
+    {
+        var services = new ServiceCollection();
+        services.AddMediatR(cfg =>
+        {
+            cfg.RegisterServicesFromAssemblyContaining<Notification>();
+            cfg.NotificationPublisherType = typeof(TaskWhenAllPublisher);
+        });
+        var serviceProvider = services.BuildServiceProvider();
+
+        var mediator = serviceProvider.GetRequiredService<IMediator>();
+
+        var timer = new Stopwatch();
+        timer.Start();
+
+        await mediator.Publish(new Notification());
+
+        timer.Stop();
+        
+        timer.ElapsedMilliseconds.ShouldBeLessThan(750);
+        
+        _output.WriteLine(timer.ElapsedMilliseconds.ToString());
+    }
 }
\ No newline at end of file