feat: added UseFor generic replacement helper method

Author: egil

src/bunit.core/ComponentFactories/ComponentFactoryCollectionExtensions.cs

@@ -80,6 +80,26 @@ public static ComponentFactoryCollection UseStubFor(this ComponentFactoryCollect
 			factories.Add(new StubComponentFactory(componentTypePredicate, options ?? StubOptions.Default));
 			return factories;
 		}
+
+		/// <summary>
+		/// Configures bUnit to replace all components of type <typeparamref name="TComponent"/> with a component
+		/// of type <typeparamref name="TReplacementComponent"/>.
+		/// </summary>
+		/// <typeparam name="TComponent">Type of component to replace.</typeparam>
+		/// <typeparam name="TReplacementComponent">Type of component to replace with.</typeparam>
+		/// <param name="factories">The bUnit <see cref="ComponentFactoryCollection"/> to configure.</param>
+		/// <returns>A <see cref="ComponentFactoryCollection"/>.</returns>
+		public static ComponentFactoryCollection UseFor<TComponent, TReplacementComponent>(this ComponentFactoryCollection factories)
+			where TComponent : IComponent
+			where TReplacementComponent : IComponent
+		{
+			if (factories is null)
+				throw new ArgumentNullException(nameof(factories));
+
+			factories.Add(new GenericComponentFactory<TComponent, TReplacementComponent>());
+
+			return factories;
+		}
 	}
 }
 #endif

src/bunit.core/ComponentFactories/GenericComponentFactory{TComponent,TReplacementComponent}.cs

@@ -0,0 +1,17 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Components;
+
+namespace Bunit.ComponentFactories
+{
+	internal sealed class GenericComponentFactory<TComponent, TReplacementComponent> : IComponentFactory
+		where TComponent : IComponent
+		where TReplacementComponent : IComponent
+	{
+		public bool CanCreate(Type componentType) => componentType == typeof(TComponent);
+		public IComponent Create(Type componentType) => (IComponent)Activator.CreateInstance(typeof(TReplacementComponent))!;
+	}
+}

tests/bunit.core.tests/ComponentFactories/GenericComponentFactoryTest.cs

@@ -0,0 +1,42 @@
+#if NET5_0_OR_GREATER
+using System;
+using System.Threading.Tasks;
+using Bunit.TestAssets.SampleComponents;
+using Microsoft.AspNetCore.Components;
+using Microsoft.AspNetCore.Components.Rendering;
+using Shouldly;
+using Xunit;
+
+namespace Bunit.ComponentFactories
+{
+	public class GenericComponentFactoryTest : TestContext
+	{
+		[Fact(DisplayName = "UseFor throws when factories is null")]
+		public void Test001()
+			=> Should.Throw<ArgumentNullException>(() => ComponentFactoryCollectionExtensions.UseFor<Simple1, FakeSimple1>(null));
+
+		[Fact(DisplayName = "UseFor<TComponent, TReplacementComponent> replaces components of type TComponent with TReplacementComponent")]
+		public void Test002()
+		{
+			ComponentFactories.UseFor<Simple1, FakeSimple1>();
+
+			var cut = RenderComponent<RefToSimple1Child>();
+
+			cut.MarkupMatches(@"<div id=""ref-status"">Has ref = True</div>");
+		}
+
+		private class FakeSimple1 : Simple1
+		{
+			protected override void OnInitialized() { }
+			protected override Task OnInitializedAsync() => Task.CompletedTask;
+			public override Task SetParametersAsync(ParameterView parameters) => Task.CompletedTask;
+			protected override void OnParametersSet() { }
+			protected override Task OnParametersSetAsync() => Task.CompletedTask;
+			protected override void BuildRenderTree(RenderTreeBuilder builder) { }
+			protected override bool ShouldRender() => false;
+			protected override void OnAfterRender(bool firstRender) { }
+			protected override Task OnAfterRenderAsync(bool firstRender) => Task.CompletedTask;
+		}
+	}
+}
+#endif