added test

Author: niemyjski

src/Platforms/Exceptionless.AspNetCore/ExceptionlessExtensions.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.Linq;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Http;
 using Exceptionless.AspNetCore;
@@ -19,7 +20,10 @@ public static class ExceptionlessExtensions {
         /// </summary>
         public static IServiceCollection AddExceptionless(this IServiceCollection services) {
             services.AddHttpContextAccessor();
-            services.AddExceptionHandler<ExceptionlessExceptionHandler>();
+            if (!services.Any(descriptor =>
+                    descriptor.ServiceType == typeof(IExceptionHandler) &&
+                    descriptor.ImplementationType == typeof(ExceptionlessExceptionHandler)))
+                services.AddExceptionHandler<ExceptionlessExceptionHandler>();
             return services;
         }
 

test/Exceptionless.Tests/Platforms/AspNetCoreExceptionCaptureTests.cs

@@ -69,6 +69,40 @@ public void OnNext_WhenUnhandledExceptionEventIsPublished_CapturesUnhandledExcep
             Assert.True(submission.IsUnhandledError);
         }
 
+        [Fact]
+        public void OnNext_WhenHostingDiagnosticsUnhandledExceptionEventIsPublished_CapturesUnhandledException() {
+            // Arrange
+            var submittingEvents = new List<EventSubmittingEventArgs>();
+            var client = CreateClient(submittingEvents);
+            var context = CreateHttpContext();
+            var exception = new InvalidOperationException("unhandled");
+            var listener = new ExceptionlessDiagnosticListener(client);
+
+            // Act
+            listener.OnNext(new KeyValuePair<string, object>("Microsoft.AspNetCore.Hosting.Diagnostics.UnhandledException", new {
+                httpContext = context,
+                exception
+            }));
+
+            // Assert
+            var submission = Assert.Single(submittingEvents);
+            Assert.True(submission.IsUnhandledError);
+        }
+
+        [Fact]
+        public void OnNext_WhenMiddlewareExceptionPayloadIsNull_DoesNotThrowOrCaptureException() {
+            // Arrange
+            var submittingEvents = new List<EventSubmittingEventArgs>();
+            var client = CreateClient(submittingEvents);
+            var listener = new ExceptionlessDiagnosticListener(client);
+
+            // Act
+            listener.OnNext(new KeyValuePair<string, object>("Microsoft.AspNetCore.MiddlewareAnalysis.MiddlewareException", null));
+
+            // Assert
+            Assert.Empty(submittingEvents);
+        }
+
         [Fact]
         public async Task Invoke_WhenResponseStatusIsNotFound_SubmitsNotFoundEvent() {
             // Arrange