Add a new UseKestel API to the WebApplicationFactory

src/Mvc/Mvc.Testing/src/Microsoft.AspNetCore.Mvc.Testing.csproj

@@ -13,6 +13,7 @@
   <ItemGroup>
     <Reference Include="Microsoft.AspNetCore.TestHost" />
     <Reference Include="Microsoft.AspNetCore.Mvc.Core" />
+    <Reference Include="Microsoft.AspNetCore.Server.Kestrel" />
     <Reference Include="Microsoft.Extensions.DependencyModel" />
     <Reference Include="Microsoft.Extensions.Hosting" />
     <Reference Include="Microsoft.Extensions.HostFactoryResolver.Sources" />

src/Mvc/Mvc.Testing/src/PublicAPI.Unshipped.txt

@@ -1 +1,5 @@
 #nullable enable
+*REMOVED*Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.Server.get -> Microsoft.AspNetCore.TestHost.TestServer!
+Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.Server.get -> Microsoft.AspNetCore.TestHost.TestServer?
+Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.UseKestrel() -> void
+virtual Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.CreateHandler() -> System.Net.Http.HttpMessageHandler!

src/Mvc/Mvc.Testing/src/Resources.resx

@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <root>
   <!-- 
     Microsoft ResX Schema 
@@ -126,4 +126,7 @@
   <data name="MissingDepsFile" xml:space="preserve">
     <value>Can't find '{0}'. This file is required for functional tests to run properly. There should be a copy of the file on your source project bin folder. If that is not the case, make sure that the property PreserveCompilationContext is set to true on your project file. E.g '&lt;PreserveCompilationContext&gt;true&lt;/PreserveCompilationContext&gt;'. For functional tests to work they need to either run from the build output folder or the {1} file from your application's output directory must be copied to the folder where the tests are running on. A common cause for this error is having shadow copying enabled when the tests run.</value>
   </data>
+  <data name="ServerNotInitialized" xml:space="preserve">
+    <value>Server hasn't been initialized yet. Plase intialized the server first before trying to create a client.</value>
+  </data>
 </root>

src/Mvc/Mvc.Testing/src/WebApplicationFactory.cs

@@ -1,14 +1,14 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Net.Http;
 using System.Reflection;
 using System.Text.Json;
 using System.Text.Json.Serialization;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Hosting.Server;
+using Microsoft.AspNetCore.Hosting.Server.Features;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
@@ -24,11 +24,14 @@
 /// Typically the Startup or Program classes can be used.</typeparam>
 public partial class WebApplicationFactory<TEntryPoint> : IDisposable, IAsyncDisposable where TEntryPoint : class
 {
+    private bool _useKestrel;
     private bool _disposed;
     private bool _disposedAsync;
     private TestServer? _server;
     private IHost? _host;
     private Action<IWebHostBuilder> _configuration;
+    private IWebHost? _webHost;
+    private Uri _webHostAddress;
     private readonly List<HttpClient> _clients = new();
     private readonly List<WebApplicationFactory<TEntryPoint>> _derivedFactories = new();
 
@@ -55,7 +58,7 @@
     /// <typeparamref name="TEntryPoint" /> will be loaded as application assemblies.
     /// </para>
     /// </summary>
     public WebApplicationFactory()
     {
         _configuration = ConfigureWebHost;
     }
@@ -71,7 +74,7 @@
     /// <summary>
     /// Gets the <see cref="TestServer"/> created by this <see cref="WebApplicationFactory{TEntryPoint}"/>.
     /// </summary>
-    public TestServer Server
+    public TestServer? Server
     {
         get
         {
@@ -88,7 +91,12 @@
         get
         {
             EnsureServer();
-            return _host?.Services ?? _server.Host.Services;
+            if (_useKestrel)
+            {
+                return _webHost!.Services;
+            }
+
+            return _host?.Services ?? _server!.Host.Services;
         }
     }
 
@@ -136,10 +144,24 @@
         return factory;
     }
 
-    [MemberNotNull(nameof(_server))]
+    /// <summary>
+    /// Configures the factory to use Kestrel as the server.
+    /// </summary>
+    public void UseKestrel()
+    {
+        _useKestrel = true;
+    }
+
+    private static IWebHost CreateKestrelServer(IWebHostBuilder builder)
+    {
+        var host = builder.UseKestrel().Build();
+        host.Start();
+        return host;
+    }
+
     private void EnsureServer()
     {
-        if (_server != null)
+        if (_server != null || _webHost != null)
         {
             return;
         }
@@ -197,21 +219,45 @@
         {
             SetContentRoot(builder);
             _configuration(builder);
-            _server = CreateServer(builder);
+            if (_useKestrel)
+            {
+                _webHost = CreateKestrelServer(builder);
+
+                var serverAddressFeature = _webHost.ServerFeatures.Get<IServerAddressesFeature>();
+                if (serverAddressFeature?.Addresses.Count > 0)
+                {
+                    // Store the web host address as it's going to be used every time a client is created to communicate to the server
+                    _webHostAddress = new Uri(serverAddressFeature.Addresses.Last());
+                    ClientOptions.BaseAddress = _webHostAddress;
+                }
+            }
+            else
+            {
+                _server = CreateServer(builder);
+            }
         }
     }
 
-    [MemberNotNull(nameof(_server))]
     private void ConfigureHostBuilder(IHostBuilder hostBuilder)
     {
         hostBuilder.ConfigureWebHost(webHostBuilder =>
         {
             SetContentRoot(webHostBuilder);
             _configuration(webHostBuilder);
-            webHostBuilder.UseTestServer();
+            if (!_useKestrel)
+            {
+                webHostBuilder.UseTestServer();
+            }
+            else
+            {
+                webHostBuilder.UseKestrel();
+            }
         });
         _host = CreateHost(hostBuilder);
-        _server = (TestServer)_host.Services.GetRequiredService<IServer>();
+        if (!_useKestrel)
+        {
+            _server = (TestServer)_host.Services.GetRequiredService<IServer>();
+        }
     }
 
     private void SetContentRoot(IWebHostBuilder builder)
@@ -455,8 +501,19 @@
     /// redirects and handles cookies.
     /// </summary>
     /// <returns>The <see cref="HttpClient"/>.</returns>
-    public HttpClient CreateClient() =>
-        CreateClient(ClientOptions);
+    public HttpClient CreateClient()
+    {
+        var client = CreateClient(ClientOptions);
+
+        if (_useKestrel)
+        {
+            // Have to do this, as the ClientOptions.BaseAddress will be set to poitn to the kestrel server,
+            // and it may not match the original base address value.
+            client.BaseAddress = ClientOptions.BaseAddress;
+        }
+
+        return client;
+    }
 
     /// <summary>
     /// Creates an instance of <see cref="HttpClient"/> that automatically follows
@@ -481,7 +538,19 @@
         HttpClient client;
         if (handlers == null || handlers.Length == 0)
         {
-            client = _server.CreateClient();
+            if (_useKestrel)
+            {
+                client = new HttpClient();
+            }
+            else
+            {
+                if (_server is null)
+                {
+                    throw new InvalidOperationException(Resources.ServerNotInitialized);
+                }
+
+                client = _server.CreateClient();
+            }
         }
         else
         {
@@ -490,7 +559,7 @@
                 handlers[i - 1].InnerHandler = handlers[i];
             }
 
-            var serverHandler = _server.CreateHandler();
+            var serverHandler = CreateHandler();
             handlers[^1].InnerHandler = serverHandler;
 
             client = new HttpClient(handlers[0]);
@@ -503,6 +572,25 @@
         return client;
     }
 
+    /// <summary>
+    /// Creates a custom <see cref="HttpMessageHandler" /> for processing HTTP requests/responses with the test server.
+    /// </summary>
+
+    protected virtual HttpMessageHandler CreateHandler()
+    {
+        if (_useKestrel)
+        {
+            return new HttpClientHandler();
+        }
+
+        if (_server is null)
+        {
+            throw new InvalidOperationException(Resources.ServerNotInitialized);
+        }
+
+        return _server.CreateHandler();
+    }
+
     /// <summary>
     /// Configures <see cref="HttpClient"/> instances created by this <see cref="WebApplicationFactory{TEntryPoint}"/>.
     /// </summary>
@@ -511,7 +599,19 @@
     {
         ArgumentNullException.ThrowIfNull(client);
 
-        client.BaseAddress = new Uri("http://localhost");
+        if (_useKestrel)
+        {
+            if (_webHost is null)
+            {
+                throw new InvalidOperationException(Resources.ServerNotInitialized);
+            }
+
+            client.BaseAddress = _webHostAddress;
+        }
+        else
+        {
+            client.BaseAddress = new Uri("http://localhost");
+        }
     }
 
     /// <summary>

src/Mvc/test/Mvc.FunctionalTests/KestrelBasedWapFactory.cs

@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Microsoft.AspNetCore.Mvc.Testing;
+
+namespace Microsoft.AspNetCore.Mvc.FunctionalTests;
+
+public class KestrelBasedWapFactory : WebApplicationFactory<SimpleWebSite.Startup>
+{
+    public KestrelBasedWapFactory() : base()
+    {
+        this.UseKestrel();
+    }
+}

src/Mvc/test/Mvc.FunctionalTests/RealServerBackedIntegrationTests.cs

@@ -0,0 +1,40 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Net;
+using System.Net.Http.Headers;
+
+namespace Microsoft.AspNetCore.Mvc.FunctionalTests;
+
+public class RealServerBackedIntegrationTests : IClassFixture<KestrelBasedWapFactory>
+{
+    public KestrelBasedWapFactory Factory { get; }
+
+    public RealServerBackedIntegrationTests(KestrelBasedWapFactory factory)
+    {
+        Factory = factory;
+    }
+
+    [Fact]
+    public async Task RetrievesDataFromRealServer()
+    {
+        // Arrange
+        var expectedMediaType = MediaTypeHeaderValue.Parse("application/json; charset=utf-8");
+
+        // Act
+        var client = Factory.CreateClient();
+        var response = await client.GetAsync("/");
+        var responseContent = await response.Content.ReadAsStringAsync();
+
+        // Assert
+        Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+        Assert.Equal(expectedMediaType, response.Content.Headers.ContentType);
+
+        Assert.Equal(5000, client.BaseAddress.Port);
+
+        Assert.Contains("first", responseContent);
+        Assert.Contains("second", responseContent);
+        Assert.Contains("wall", responseContent);
+        Assert.Contains("floor", responseContent);
+    }
+}