unit test exception.

Author: ilonatommy

src/Components/Endpoints/src/Rendering/EndpointHtmlRenderer.EventDispatch.cs

@@ -79,7 +79,7 @@ private Task ReturnErrorResponse(string detailedMessage)
             : Task.CompletedTask;
     }
 
-    private async Task SetNotFoundResponseAsync(string baseUri, NotFoundEventArgs args)
+    internal async Task SetNotFoundResponseAsync(string baseUri, NotFoundEventArgs args)
     {
         if (_httpContext.Response.HasStarted)
         {

src/Components/Endpoints/src/Rendering/EndpointHtmlRenderer.cs

@@ -64,7 +64,7 @@ public EndpointHtmlRenderer(IServiceProvider serviceProvider, ILoggerFactory log
 
     internal HttpContext? HttpContext => _httpContext;
 
-    private void SetHttpContext(HttpContext httpContext)
+    internal void SetHttpContext(HttpContext httpContext)
     {
         if (_httpContext is null)
         {
@@ -87,7 +87,8 @@ internal async Task InitializeStandardComponentServicesAsync(
 
         if (navigationManager != null)
         {
-            navigationManager.OnNotFound += async (sender, args) => await SetNotFoundResponseAsync(navigationManager.BaseUri, args);
+            navigationManager.OnNotFound += async (sender, args) =>
+                await GetErrorHandledTask(SetNotFoundResponseAsync(navigationManager.BaseUri, args));
         }
 
         var authenticationStateProvider = httpContext.RequestServices.GetService<AuthenticationStateProvider>();

src/Components/Endpoints/test/EndpointHtmlRendererTest.cs

@@ -1,9 +1,11 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System;
 using System.Text.Encodings.Web;
 using System.Text.Json;
 using System.Text.RegularExpressions;
+using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Components.Endpoints.Forms;
 using Microsoft.AspNetCore.Components.Endpoints.Tests.TestComponents;
 using Microsoft.AspNetCore.Components.Forms;
@@ -12,6 +14,7 @@
 using Microsoft.AspNetCore.Components.Reflection;
 using Microsoft.AspNetCore.Components.Rendering;
 using Microsoft.AspNetCore.Components.RenderTree;
+using Microsoft.AspNetCore.Components.Routing;
 using Microsoft.AspNetCore.Components.Test.Helpers;
 using Microsoft.AspNetCore.Components.Web;
 using Microsoft.AspNetCore.DataProtection;
@@ -934,6 +937,28 @@ await renderer.PrerenderComponentAsync(
         Assert.Equal("http://localhost/redirect", ctx.Response.Headers.Location);
     }
 
+    [Fact]
+    public async Task Renderer_WhenNoNotFoundPathProvided_Throws()
+    {
+        // Arrange
+        var httpContext = GetHttpContext();
+        var responseMock = new Mock<IHttpResponseFeature>();
+        responseMock.Setup(r => r.HasStarted).Returns(true);
+        responseMock.Setup(r => r.Headers).Returns(new HeaderDictionary());
+        httpContext.Features.Set(responseMock.Object);
+        var renderer = GetEndpointHtmlRenderer();
+        httpContext.Items[nameof(StatusCodePagesOptions)] = null; // simulate missing re-execution route
+
+        var component = new NotFoundComponent();
+        var id = renderer.AssignRootComponentId(component);
+        var exception = await Assert.ThrowsAsync<InvalidOperationException>(async () =>
+            await renderer.SetNotFoundResponseAsync(httpContext, new NotFoundEventArgs(""))
+        );
+        string expectedError = "The NotFoundPage route must be specified or re-execution middleware has to be set to render NotFoundPage when the response has started.";
+
+        Assert.Equal(expectedError, exception.Message);
+    }
+
     [Fact]
     public async Task CanRender_AsyncComponent()
     {
@@ -1802,6 +1827,12 @@ protected override void ProcessPendingRender()
             _rendererIsStopped = true;
             base.SignalRendererToFinishRendering();
         }
+
+        public async Task SetNotFoundResponseAsync(HttpContext httpContext, NotFoundEventArgs args)
+        {
+            SetHttpContext(httpContext);
+            await SetNotFoundResponseAsync(httpContext.Request.PathBase, args);
+        }
     }
 
     private HttpContext GetHttpContext(HttpContext context = null)