Solve 404 error in unit test

test/OpenTelemetry.Instrumentation.AspNetCore.Tests/BasicTests.cs

@@ -960,6 +960,7 @@ public async Task DiagnosticSourceExceptionCallBackIsNotReceivedForExceptionsHan
         int numberOfUnSubscribedEvents = 0;
         int numberOfSubscribedEvents = 0;
         int numberOfExceptionCallbacks = 0;
+        bool exceptionHandled = false;
 
         // configure SDK
         this.tracerProvider = Sdk.CreateTracerProviderBuilder()
@@ -1004,18 +1005,18 @@ public async Task DiagnosticSourceExceptionCallBackIsNotReceivedForExceptionsHan
                 })
                 .Build();
 
+        TestMiddleware.Create(builder => builder
+            .UseExceptionHandler(handler =>
+                handler.Run(async (ctx) =>
+                {
+                    exceptionHandled = true;
+                    await ctx.Response.WriteAsync("handled");
+                })));
+
         using (var client = this.factory
             .WithWebHostBuilder(builder =>
             {
                 builder.ConfigureLogging(loggingBuilder => loggingBuilder.ClearProviders());
-                builder.Configure(app => app
-                    .UseExceptionHandler(handler =>
-                    {
-                        handler.Run(async (ctx) =>
-                        {
-                            await ctx.Response.WriteAsync("handled");
-                        });
-                    }));
             })
             .CreateClient())
         {
@@ -1033,6 +1034,7 @@ public async Task DiagnosticSourceExceptionCallBackIsNotReceivedForExceptionsHan
         Assert.Equal(0, numberOfExceptionCallbacks);
         Assert.Equal(0, numberOfUnSubscribedEvents);
         Assert.Equal(2, numberOfSubscribedEvents);
+        Assert.True(exceptionHandled);
     }
 
     public void Dispose()

test/TestApp.AspNetCore/Program.cs

@@ -60,6 +60,8 @@ public static void Main(string[] args)
 
         app.UseMiddleware<ActivityMiddleware>();
 
+        app.AddTestMiddleware();
+
         app.Run();
     }
 }

test/TestApp.AspNetCore/TestMiddleware.cs

@@ -0,0 +1,37 @@
+// <copyright file="TestMiddleware.cs" company="OpenTelemetry Authors">
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// </copyright>
+
+namespace TestApp.AspNetCore;
+
+public static class TestMiddleware
+{
+    private static readonly AsyncLocal<Action<IApplicationBuilder>?> Current = new();
+
+    public static IApplicationBuilder AddTestMiddleware(this IApplicationBuilder builder)
+    {
+        if (Current.Value is { } configure)
+        {
+            configure(builder);
+        }
+
+        return builder;
+    }
+
+    public static void Create(Action<IApplicationBuilder> action)
+    {
+        Current.Value = action;
+    }
+}