Added a TypeRegistrar to CommandAppTester

exposed as a public property.
For convenience, and to keep the similarity to the real CommandApp
it is also available in the ctor of CommandAppTester.

src/Spectre.Console.Testing/Cli/CommandAppTester.cs

@@ -11,6 +11,20 @@ namespace Spectre.Console.Testing
         private Action<CommandApp>? _appConfiguration;
         private Action<IConfigurator>? _configuration;
 
+        /// <summary>
+        /// Initializes a new instance of the <see cref="CommandAppTester"/> class.
+        /// </summary>
+        /// <param name="registrar">The registrar.</param>
+        public CommandAppTester(ITypeRegistrar? registrar = null)
+        {
+            Registrar = registrar;
+        }
+
+        /// <summary>
+        /// Gets or sets the Registrar to use in the CommandApp.
+        /// </summary>
+        public ITypeRegistrar? Registrar { get; set; }
+
         /// <summary>
         /// Sets the default command.
         /// </summary>
@@ -88,7 +102,7 @@ namespace Spectre.Console.Testing
             CommandContext? context = null;
             CommandSettings? settings = null;
 
-            var app = new CommandApp();
+            var app = new CommandApp(Registrar);
             _appConfiguration?.Invoke(app);
 
             if (_configuration != null)

test/Spectre.Console.Tests/Unit/Cli/CommandAppTests.Injection.cs

@@ -1,3 +1,5 @@
+using System;
+using System.Collections.Generic;
 using Shouldly;
 using Spectre.Console.Testing;
 using Spectre.Console.Tests.Data;
@@ -62,6 +64,36 @@ namespace Spectre.Console.Tests.Unit.Cli
                     injected.Age.ShouldBe(35);
                 });
             }
+
+            [Fact]
+            public void Should_Inject_Dependency_Using_A_Given_Registrar()
+            {
+                // Given
+                var dependency = new FakeDependency();
+                var registrar = new FakeTypeRegistrar { TypeResolverFactory = FakeTypeResolver.Factory };
+                registrar.RegisterInstance(typeof(FakeDependency), dependency);
+                var app = new CommandAppTester(registrar);
+
+                app.SetDefaultCommand<GenericCommand<InjectSettings>>();
+                app.Configure(config => config.PropagateExceptions());
+
+                // When
+                var result = app.Run(new[]
+                {
+                    "--name", "foo",
+                    "--age", "35",
+                });
+
+                // Then
+                result.ExitCode.ShouldBe(0);
+                result.Settings.ShouldBeOfType<InjectSettings>().And(injected =>
+                {
+                    injected.ShouldNotBeNull();
+                    injected.Fake.ShouldBeSameAs(dependency);
+                    injected.Name.ShouldBe("Hello foo");
+                    injected.Age.ShouldBe(35);
+                });
+            }
         }
     }
 }

test/Spectre.Console.Tests/Utilities/FakeTypeRegistrar.cs

@@ -8,6 +8,7 @@ namespace Spectre.Console.Testing
     {
         public Dictionary<Type, List<Type>> Registrations { get; }
         public Dictionary<Type, List<object>> Instances { get; }
+        public Func<Dictionary<Type, List<Type>>, Dictionary<Type, List<object>>, ITypeResolver> TypeResolverFactory { get; set; }
 
         public FakeTypeRegistrar()
         {
@@ -50,7 +51,7 @@ namespace Spectre.Console.Testing
 
         public ITypeResolver Build()
         {
-            return null;
+            return TypeResolverFactory?.Invoke(Registrations, Instances);
         }
     }
 }

test/Spectre.Console.Tests/Utilities/FakeTypeResolver.cs

@@ -0,0 +1,41 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Spectre.Console.Cli;
+
+namespace Spectre.Console.Testing
+{
+    public sealed class FakeTypeResolver : ITypeResolver
+    {
+        private readonly Dictionary<Type, List<Type>> _registrations;
+        private readonly Dictionary<Type, List<object>> _instances;
+
+        public FakeTypeResolver(
+            Dictionary<Type, List<Type>> registrations,
+            Dictionary<Type, List<object>> instances)
+        {
+            _registrations = registrations ?? throw new ArgumentNullException(nameof(registrations));
+            _instances = instances ?? throw new ArgumentNullException(nameof(instances));
+        }
+
+        public static Func<Dictionary<Type, List<Type>>, Dictionary<Type, List<object>>, ITypeResolver> Factory =>
+            (r, i) => new FakeTypeResolver(r, i);
+
+        public object Resolve(Type type)
+        {
+            if (_instances.TryGetValue(type, out var instances))
+            {
+                return instances.FirstOrDefault();
+            }
+
+            if (_registrations.TryGetValue(type, out var registrations))
+            {
+                return registrations.Count == 0 
+                    ? null 
+                    : Activator.CreateInstance(type);
+            }
+
+            return null;
+        }
+    }
+}