Fix mock authentication in ASP.NET Core integration tests docs (#36861)

* Initial plan

* Fix mock authentication in integration tests - explicitly set DefaultAuthenticateScheme and DefaultChallengeScheme

Co-authored-by: meaghanlewis <10103121+meaghanlewis@users.noreply.github.com>

* Remove accidentally committed nuget.exe binary

Co-authored-by: meaghanlewis <10103121+meaghanlewis@users.noreply.github.com>

* Revert .gitignore change

Co-authored-by: meaghanlewis <10103121+meaghanlewis@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: meaghanlewis <10103121+meaghanlewis@users.noreply.github.com>

Author: Copilot

aspnetcore/test/integration-tests.md

@@ -5,7 +5,7 @@ description: Learn how integration tests ensure that an app's components functio
 monikerRange: '>= aspnetcore-3.1'
 ms.author: tdykstra
 ms.custom: mvc
-ms.date: 3/24/2025
+ms.date: 03/10/2026
 uid: test/integration-tests
 zone_pivot_groups: unit-testing-framework
 ---

aspnetcore/test/integration-tests/includes/integration-tests9.md

@@ -369,21 +369,21 @@ The test app can mock an <xref:Microsoft.AspNetCore.Authentication.Authenticatio
 
 :::zone-end
 
-The `TestAuthHandler` is called to authenticate a user when the authentication scheme is set to `TestScheme` where `AddAuthentication` is registered for `ConfigureTestServices`. It's important for the `TestScheme` scheme to match the scheme your app expects. Otherwise, authentication won't work.
+The `TestAuthHandler` is called to authenticate a user when the authentication scheme is set to `TestScheme` where `AddAuthentication` is registered for `ConfigureTestServices`. `DefaultAuthenticateScheme` and `DefaultChallengeScheme` are explicitly set to `TestScheme` to ensure the test handler overrides any authentication configuration set by the app. It's important for the `TestScheme` scheme to match the scheme your app expects. Otherwise, authentication won't work.
 
 :::zone pivot="xunit"
 
-:::code language="csharp" source="~/test/integration-tests/snippets/xunit/IntegrationTests/AuthTests.cs" id="snippet3" highlight="7-12":::
+:::code language="csharp" source="~/test/integration-tests/snippets/xunit/IntegrationTests/AuthTests.cs" id="snippet3" highlight="7-16":::
 
 :::zone-end
 :::zone pivot="mstest"
 
-:::code language="csharp" source="~/test/integration-tests/snippets/mstest/IntegrationTests/AuthTests.cs" id="snippet3" highlight="7-12":::
+:::code language="csharp" source="~/test/integration-tests/snippets/mstest/IntegrationTests/AuthTests.cs" id="snippet3" highlight="7-16":::
 
 :::zone-end
 :::zone pivot="nunit"
 
-:::code language="csharp" source="~/test/integration-tests/snippets/nunit/IntegrationTests/AuthTests.cs" id="snippet3" highlight="7-12":::
+:::code language="csharp" source="~/test/integration-tests/snippets/nunit/IntegrationTests/AuthTests.cs" id="snippet3" highlight="7-16":::
 
 :::zone-end
 

aspnetcore/test/integration-tests/snippets/mstest/IntegrationTests/AuthTests.cs

@@ -112,7 +112,11 @@ public async Task Get_SecurePageIsReturnedForAnAuthenticatedUser()
         {
             builder.ConfigureTestServices(services =>
             {
-                services.AddAuthentication(defaultScheme: "TestScheme")
+                services.AddAuthentication(options =>
+                    {
+                        options.DefaultAuthenticateScheme = "TestScheme";
+                        options.DefaultChallengeScheme = "TestScheme";
+                    })
                     .AddScheme<AuthenticationSchemeOptions, TestAuthHandler>(
                         "TestScheme", options => { });
             });

aspnetcore/test/integration-tests/snippets/nunit/IntegrationTests/AuthTests.cs

@@ -110,7 +110,11 @@ public async Task Get_SecurePageIsReturnedForAnAuthenticatedUser()
         {
             builder.ConfigureTestServices(services =>
             {
-                services.AddAuthentication(defaultScheme: "TestScheme")
+                services.AddAuthentication(options =>
+                    {
+                        options.DefaultAuthenticateScheme = "TestScheme";
+                        options.DefaultChallengeScheme = "TestScheme";
+                    })
                     .AddScheme<AuthenticationSchemeOptions, TestAuthHandler>(
                         "TestScheme", options => { });
             });

aspnetcore/test/integration-tests/snippets/xunit/IntegrationTests/AuthTests.cs

@@ -106,7 +106,11 @@ public async Task Get_SecurePageIsReturnedForAnAuthenticatedUser()
             {
                 builder.ConfigureTestServices(services =>
                 {
-                    services.AddAuthentication(defaultScheme: "TestScheme")
+                    services.AddAuthentication(options =>
+                        {
+                            options.DefaultAuthenticateScheme = "TestScheme";
+                            options.DefaultChallengeScheme = "TestScheme";
+                        })
                         .AddScheme<AuthenticationSchemeOptions, TestAuthHandler>(
                             "TestScheme", options => { });
                 });