- Created an ITestServer abstraction to replace the TestServer dependency with from in the WebApplicationFactory.

- Updated the WebApplicationFactory to depend on the ITestServer abstraction

Author: mkArtakMSFT

src/Hosting/TestHost/src/ITestServer.cs

@@ -0,0 +1,31 @@
+// 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.Http;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Hosting.Server;
+
+namespace Microsoft.AspNetCore.TestHost;
+
+/// <summary>
+/// A contract for a test server implementation.
+/// </summary>
+public interface ITestServer : IServer
+{
+    /// <summary>
+    /// Gets the web host associated with the test server.
+    /// </summary>
+    IWebHost Host { get; }
+
+    /// <summary>
+    /// Creates a new <see cref="HttpMessageHandler"/> for processing HTTP requests against the test server.
+    /// </summary>
+    /// <returns>A new <see cref="HttpMessageHandler"/> instance.</returns>
+    HttpMessageHandler CreateHandler();
+
+    /// <summary>
+    /// Creates a new <see cref="HttpClient"/> for processing HTTP requests against the test server.
+    /// </summary>
+    /// <returns></returns>
+    HttpClient CreateClient();
+}

src/Hosting/TestHost/src/PublicAPI.Unshipped.txt

@@ -1 +1,5 @@
 #nullable enable
+Microsoft.AspNetCore.TestHost.ITestServer
+Microsoft.AspNetCore.TestHost.ITestServer.CreateClient() -> System.Net.Http.HttpClient!
+Microsoft.AspNetCore.TestHost.ITestServer.CreateHandler() -> System.Net.Http.HttpMessageHandler!
+Microsoft.AspNetCore.TestHost.ITestServer.Host.get -> Microsoft.AspNetCore.Hosting.IWebHost!

src/Hosting/TestHost/src/TestServer.cs

@@ -14,7 +14,7 @@ namespace Microsoft.AspNetCore.TestHost;
 /// <summary>
 /// An <see cref="IServer"/> implementation for executing tests.
 /// </summary>
-public class TestServer : IServer
+public class TestServer : ITestServer
 {
     private readonly IWebHost? _hostInstance;
     private bool _disposed;

src/Mvc/Mvc.Testing/src/PublicAPI.Shipped.txt

@@ -16,7 +16,6 @@ Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.CreateDefaul
 Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.CreateDefaultClient(System.Uri! baseAddress, params System.Net.Http.DelegatingHandler![]! handlers) -> System.Net.Http.HttpClient!
 Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.Dispose() -> void
 Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.Factories.get -> System.Collections.Generic.IReadOnlyList<Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint!>!>!
-Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.Server.get -> Microsoft.AspNetCore.TestHost.TestServer!
 Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.WebApplicationFactory() -> void
 Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.WithWebHostBuilder(System.Action<Microsoft.AspNetCore.Hosting.IWebHostBuilder!>! configuration) -> Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint!>!
 Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactoryClientOptions
@@ -41,7 +40,6 @@ virtual Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.Conf
 virtual Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.ConfigureWebHost(Microsoft.AspNetCore.Hosting.IWebHostBuilder! builder) -> void
 virtual Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.CreateHost(Microsoft.Extensions.Hosting.IHostBuilder! builder) -> Microsoft.Extensions.Hosting.IHost!
 virtual Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.CreateHostBuilder() -> Microsoft.Extensions.Hosting.IHostBuilder?
-virtual Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.CreateServer(Microsoft.AspNetCore.Hosting.IWebHostBuilder! builder) -> Microsoft.AspNetCore.TestHost.TestServer!
 virtual Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.CreateWebHostBuilder() -> Microsoft.AspNetCore.Hosting.IWebHostBuilder?
 virtual Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.Dispose(bool disposing) -> void
 virtual Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.DisposeAsync() -> System.Threading.Tasks.ValueTask

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

@@ -1 +1,5 @@
 #nullable enable
+Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.Initialize() -> void
+Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.Server.get -> Microsoft.AspNetCore.TestHost.TestServer?
+Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.TestServer.get -> Microsoft.AspNetCore.TestHost.ITestServer?
+virtual Microsoft.AspNetCore.Mvc.Testing.WebApplicationFactory<TEntryPoint>.CreateServer(Microsoft.AspNetCore.Hosting.IWebHostBuilder! builder) -> Microsoft.AspNetCore.TestHost.ITestServer!

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 
@@ -120,6 +120,9 @@
   <data name="InvalidAssemblyEntryPoint" xml:space="preserve">
     <value>The provided Type '{0}' does not belong to an assembly with an entry point. A common cause for this error is providing a Type from a class library.</value>
   </data>
+  <data name="InvalidTestServerConfiguration" xml:space="preserve">
+    <value>The host doesn't contain a valid ITestServer configuration.</value>
+  </data>
   <data name="MissingBuilderMethod" xml:space="preserve">
     <value>No method 'public static {0} CreateHostBuilder(string[] args)' or 'public static {1} CreateWebHostBuilder(string[] args)' found on '{2}'. Alternatively, {3} can be extended and '{4}' or '{5}' can be overridden to provide your own instance.</value>
   </data>

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

@@ -22,11 +22,16 @@ namespace Microsoft.AspNetCore.Mvc.Testing;
 /// </summary>
 /// <typeparam name="TEntryPoint">A type in the entry point assembly of the application.
 /// Typically the Startup or Program classes can be used.</typeparam>
+/// <remarks>The default behavior of the <see cref="CreateServer(IWebHostBuilder)"/> implementation
+/// creates a new <see cref="TestHost.TestServer"/> instance as an in-memory server to utilize for testing.
+/// If the developers wants, they can override the <see cref="CreateServer(IWebHostBuilder)"/> method to return a customer <see cref="ITestServer"/> implementation,
+/// and provide an adapter over a real web server, if needed. If done so, the <see cref="CreateClient()"/> and similar methods will
+/// create <see cref="HttpClient"/> instances configured to interact with the provided test server instead.</remarks>
 public partial class WebApplicationFactory<TEntryPoint> : IDisposable, IAsyncDisposable where TEntryPoint : class
 {
     private bool _disposed;
     private bool _disposedAsync;
-    private TestServer? _server;
+    private ITestServer? _server;
     private IHost? _host;
     private Action<IWebHostBuilder> _configuration;
     private readonly List<HttpClient> _clients = new();
@@ -71,11 +76,23 @@ public WebApplicationFactory()
     /// <summary>
     /// Gets the <see cref="TestServer"/> created by this <see cref="WebApplicationFactory{TEntryPoint}"/>.
     /// </summary>
-    public TestServer Server
+    [Obsolete("This property is obsolete. Consider utilizing the TestServer property instead.")]
+    public TestServer? Server
     {
         get
         {
-            EnsureServer();
+            return TestServer as TestServer;
+        }
+    }
+
+    /// <summary>
+    /// Gets the <see cref="ITestServer"/> instance created by the underyling <see cref="CreateServer(IWebHostBuilder)"/> call.
+    /// </summary>
+    public ITestServer? TestServer
+    {
+        get
+        {
+            Initialize();
             return _server;
         }
     }
@@ -87,7 +104,7 @@ public virtual IServiceProvider Services
     {
         get
         {
-            EnsureServer();
+            Initialize();
             return _host?.Services ?? _server.Host.Services;
         }
     }
@@ -136,8 +153,12 @@ internal virtual WebApplicationFactory<TEntryPoint> WithWebHostBuilderCore(Actio
         return factory;
     }
 
+    /// <summary>
+    /// Initializes the instance by configurating the host builder.
+    /// </summary>
+    /// <exception cref="InvalidOperationException">Thrown if the provided <typeparamref name="TEntryPoint"/> type has no factory method.</exception>
     [MemberNotNull(nameof(_server))]
-    private void EnsureServer()
+    public void Initialize()
     {
         if (_server != null)
         {
@@ -211,7 +232,11 @@ private void ConfigureHostBuilder(IHostBuilder hostBuilder)
             webHostBuilder.UseTestServer();
         });
         _host = CreateHost(hostBuilder);
-        _server = (TestServer)_host.Services.GetRequiredService<IServer>();
+        _server = _host.Services.GetRequiredService<IServer>() as ITestServer;
+        if (_server is null)
+        {
+            throw new InvalidOperationException(Resources.InvalidTestServerConfiguration);
+        }
     }
 
     private void SetContentRoot(IWebHostBuilder builder)
@@ -426,7 +451,7 @@ private static void EnsureDepsFile()
     /// <param name="builder">The <see cref="IWebHostBuilder"/> used to
     /// create the server.</param>
     /// <returns>The <see cref="TestServer"/> with the bootstrapped application.</returns>
-    protected virtual TestServer CreateServer(IWebHostBuilder builder) => new(builder);
+    protected virtual ITestServer CreateServer(IWebHostBuilder builder) => new TestServer(builder);
 
     /// <summary>
     /// Creates the <see cref="IHost"/> with the bootstrapped application in <paramref name="builder"/>.
@@ -476,7 +501,7 @@ public HttpClient CreateClient(WebApplicationFactoryClientOptions options) =>
     /// <returns>The <see cref="HttpClient"/>.</returns>
     public HttpClient CreateDefaultClient(params DelegatingHandler[] handlers)
     {
-        EnsureServer();
+        Initialize();
 
         HttpClient client;
         if (handlers == null || handlers.Length == 0)
@@ -606,7 +631,7 @@ public virtual async ValueTask DisposeAsync()
 
     private sealed class DelegatedWebApplicationFactory : WebApplicationFactory<TEntryPoint>
     {
-        private readonly Func<IWebHostBuilder, TestServer> _createServer;
+        private readonly Func<IWebHostBuilder, ITestServer> _createServer;
         private readonly Func<IHostBuilder, IHost> _createHost;
         private readonly Func<IWebHostBuilder?> _createWebHostBuilder;
         private readonly Func<IHostBuilder?> _createHostBuilder;
@@ -615,7 +640,7 @@ private sealed class DelegatedWebApplicationFactory : WebApplicationFactory<TEnt
 
         public DelegatedWebApplicationFactory(
             WebApplicationFactoryClientOptions options,
-            Func<IWebHostBuilder, TestServer> createServer,
+            Func<IWebHostBuilder, ITestServer> createServer,
             Func<IHostBuilder, IHost> createHost,
             Func<IWebHostBuilder?> createWebHostBuilder,
             Func<IHostBuilder?> createHostBuilder,
@@ -633,7 +658,7 @@ public DelegatedWebApplicationFactory(
             _configuration = configureWebHost;
         }
 
-        protected override TestServer CreateServer(IWebHostBuilder builder) => _createServer(builder);
+        protected override ITestServer CreateServer(IWebHostBuilder builder) => _createServer(builder);
 
         protected override IHost CreateHost(IHostBuilder builder) => _createHost(builder);
 

src/Mvc/test/Mvc.FunctionalTests/ApiExplorerTest.cs

@@ -1573,7 +1573,7 @@ public async Task ApiExplorer_LogsInvokedDescriptionProvidersOnStartup()
     [Fact]
     public void ApiExplorer_BuildsMetadataForActionWithTypedResult()
     {
-        var apiDescCollectionProvider = Factory.Server.Services.GetService<IApiDescriptionGroupCollectionProvider>();
+        var apiDescCollectionProvider = Factory.Services.GetService<IApiDescriptionGroupCollectionProvider>();
         var testGroupName = nameof(ApiExplorerWithTypedResultController).Replace("Controller", string.Empty);
         var group = apiDescCollectionProvider.ApiDescriptionGroups.Items.Where(i => i.GroupName == testGroupName).SingleOrDefault();
         Assert.NotNull(group);

src/Mvc/test/Mvc.FunctionalTests/ComponentRenderingFunctionalTests.cs

@@ -198,7 +198,7 @@ private HttpClient CreateClient(
 
         // We configure the inner handler with a handler to this TestServer instance so that calls to the
         // server can get routed properly.
-        loopHandler.InnerHandler = fixture.Server.CreateHandler();
+        loopHandler.InnerHandler = fixture.TestServer.CreateHandler();
 
         void ConfigureTestWeatherForecastService(IServiceCollection services) =>
             // We configure the test service here with an HttpClient that uses this loopback handler to talk

src/Mvc/test/Mvc.FunctionalTests/Infrastructure/MvcTestFixture.cs

@@ -42,7 +42,7 @@ protected override void ConfigureWebHost(IWebHostBuilder builder)
                 });
     }
 
-    protected override TestServer CreateServer(IWebHostBuilder builder)
+    protected override ITestServer CreateServer(IWebHostBuilder builder)
     {
         var originalCulture = CultureInfo.CurrentCulture;
         var originalUICulture = CultureInfo.CurrentUICulture;

src/Mvc/test/Mvc.FunctionalTests/TestingInfrastructureInheritanceTests.cs

@@ -141,7 +141,7 @@ protected override void ConfigureWebHost(IWebHostBuilder builder)
             base.ConfigureWebHost(builder);
         }
 
-        protected override TestServer CreateServer(IWebHostBuilder builder)
+        protected override ITestServer CreateServer(IWebHostBuilder builder)
         {
             CreateServerCalled = true;
             return base.CreateServer(builder);