Solve 404 error in unit test (#5145)

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

@@ -947,6 +947,7 @@ public sealed class BasicTests
         int numberOfUnSubscribedEvents = 0;
         int numberOfSubscribedEvents = 0;
         int numberOfExceptionCallbacks = 0;
+        bool exceptionHandled = false;
 
         // configure SDK
         this.tracerProvider = Sdk.CreateTracerProviderBuilder()
@@ -991,18 +992,18 @@ public sealed class BasicTests
                 })
                 .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())
         {
@@ -1020,6 +1021,7 @@ public sealed class BasicTests
         Assert.Equal(0, numberOfExceptionCallbacks);
         Assert.Equal(0, numberOfUnSubscribedEvents);
         Assert.Equal(2, numberOfSubscribedEvents);
+        Assert.True(exceptionHandled);
     }
 
     public void Dispose()

test/TestApp.AspNetCore/Program.cs

@@ -47,6 +47,8 @@ public class Program
 
         app.UseMiddleware<ActivityMiddleware>();
 
+        app.AddTestMiddleware();
+
         app.Run();
     }
 }

test/TestApp.AspNetCore/TestMiddleware.cs

@@ -0,0 +1,24 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+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;
+    }
+}