TestServer registers NoopHostLifetime to avoid hangs from not disposing

src/Hosting/TestHost/src/NoopHostLifetime.cs

@@ -0,0 +1,22 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.Extensions.Hosting;
+
+namespace Microsoft.AspNetCore.TestHost
+{
+    internal class NoopHostLifetime : IHostLifetime
+    {
+        public Task StopAsync(CancellationToken cancellationToken)
+        {
+            return Task.CompletedTask;
+        }
+
+        public Task WaitForStartAsync(CancellationToken cancellationToken)
+        {
+            return Task.CompletedTask;
+        }
+    }
+}

src/Hosting/TestHost/src/WebHostBuilderExtensions.cs

@@ -8,6 +8,7 @@
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Hosting.Server;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
 
 namespace Microsoft.AspNetCore.TestHost
 {
@@ -17,6 +18,7 @@ public static IWebHostBuilder UseTestServer(this IWebHostBuilder builder)
         {
             return builder.ConfigureServices(services =>
             {
+                services.AddSingleton<IHostLifetime, NoopHostLifetime>();
                 services.AddSingleton<IServer, TestServer>();
             });
         }

src/Hosting/TestHost/test/TestServerTests.cs

@@ -79,6 +79,21 @@ public async Task GenericCreateAndStartHost_GetTestClient()
             Assert.Equal(HttpStatusCode.NotFound, response.StatusCode);
         }
 
+        [Fact]
+        public async Task UseTestServerRegistersNoopHostLifetime()
+        {
+            using var host = await new HostBuilder()
+                .ConfigureWebHost(webBuilder =>
+                {
+                    webBuilder
+                        .UseTestServer()
+                        .Configure(app => { });
+                })
+                .StartAsync();
+
+            Assert.IsType<NoopHostLifetime>(host.Services.GetService<IHostLifetime>());
+        }
+
         [Fact]
         public void CreateWithDelegate()
         {