Simple fake navigation manager

CHANGELOG.md

@@ -28,7 +28,46 @@ List of new features.
 
   NOTE, a better approach is to use the `WaitForState` or `WaitForAssertion` methods, which now also throws unhandled exceptions. Using them, you do not need to set up a wait timeout explicitly.
 
-   By [@egil](https://github.com/egil) in [#310](https://github.com/egil/bUnit/issues/344).
+  By [@egil](https://github.com/egil) in [#344](https://github.com/egil/bUnit/issues/344).
+
+- Added a simple fake navigation manager, which is registered by default in bUnit's service provider. When the fake navigation manager's `NavigateTo` method is called, it does two things:  
+
+  1. Set the `Uri` property to the URI passed to the `NavigateTo` method (with the URI normalized to an absolute URI).
+  2. Raise the `LocationChanged` event with the URI passed to the `NavigateTo` method.
+
+  Lets look at an example: To verify that the `<GoesToFooOnInit>` component below calls the `NavigationManager.NavigateTo` method with the expected value, do the following:
+
+  `<GoesToFooOnInit>` component:
+
+  ```cshtml
+  @inject NavigationManager NavMan
+  @code {
+    protected override void OnInitialized()
+    {
+      NavMan.NavigateTo("foo");
+    }
+  }
+  ```
+
+  Test code:
+
+  ```csharp
+  // Arrange
+  using var ctx = new TestContext();
+  var navMan = ctx.Services.GetRequiredService<NavigationManager>();
+
+  // Act
+  var cut = ctx.RenderComponent<GoesToFooOnInit>();
+
+  // Assert
+  Assert.Equal($"{navMan.BaseUri}foo", navMan.Uri);
+  ```
+
+  Since the `foo` input argument is normalized to an absolute URI, we have to do the same normalization in our assertion. 
+
+  The fake navigation manager's `BaseUri` is set to `http://localhost/`, but it is not recommended to use that URL directly in your code. Instead create an assertion by getting that value from the `BaseUri` property, like shown in the example above.
+
+  By [@egil](https://github.com/egil) in [#345](https://github.com/egil/bUnit/pull/345).
 
 ### Changed
 List of changes in existing functionality.

src/bunit.web/Extensions/TestServiceProviderExtensions.cs

@@ -34,13 +34,15 @@ public static IServiceCollection AddDefaultTestContextServices(this IServiceColl
 			services.AddSingleton<ILoggerFactory>(NullLoggerFactory.Instance);
 			services.AddSingleton<AuthenticationStateProvider, PlaceholderAuthenticationStateProvider>();
 			services.AddSingleton<IAuthorizationService, PlaceholderAuthorizationService>();
-			services.AddSingleton<NavigationManager, PlaceholderNavigationManager>();
 			services.AddSingleton<HttpClient, PlaceholderHttpClient>();
 			services.AddSingleton<IStringLocalizer, PlaceholderStringLocalization>();
 
 			// bUnits fake JSInterop
 			services.AddSingleton<IJSRuntime>(jsInterop.JSRuntime);
 
+			// bUnits fake Navigation Manager
+			services.AddSingleton<NavigationManager, FakeNavigationManager>();
+
 			// bUnit specific services
 			services.AddSingleton<TestContextBase>(testContext);
 			services.AddSingleton<ITestRenderer, WebTestRenderer>();

src/bunit.web/TestDoubles/NavigationManager/FakeNavigationManager.cs

@@ -0,0 +1,35 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
+using Bunit.Rendering;
+using Microsoft.AspNetCore.Components;
+
+namespace Bunit.TestDoubles
+{
+	/// <summary>
+	/// Represents a fake <see cref="NavigationManager"/> that captures calls to
+	/// <see cref="NavigationManager.NavigateTo(string, bool)"/> for testing purposes.
+	/// </summary>
+	public sealed class FakeNavigationManager : NavigationManager
+	{
+		private readonly ITestRenderer renderer;
+
+		/// <summary>
+		/// Initializes a new instance of the <see cref="FakeNavigationManager"/> class.
+		/// </summary>
+		[SuppressMessage("Minor Code Smell", "S1075:URIs should not be hardcoded", Justification = "By design. Fake navigation manager defaults to local host as base URI.")]
+		public FakeNavigationManager(ITestRenderer renderer)
+		{
+			this.renderer = renderer ?? throw new ArgumentNullException(nameof(renderer));
+			Initialize("http://localhost/", "http://localhost/");
+		}
+
+		/// <inheritdoc/>
+		protected override void NavigateToCore(string uri, bool forceLoad)
+		{
+			Uri = ToAbsoluteUri(uri).ToString();
+
+			renderer.Dispatcher.InvokeAsync(
+				() => NotifyLocationChanged(isInterceptedLink: false));
+		}
+	}
+}