Return key in IConsole.ReadKey(...)

Closes #124

CliFx.Tests/ConsoleSpecs.cs

@@ -5,6 +5,7 @@ using System.Text;
 using System.Threading.Tasks;
 using CliFx.Infrastructure;
 using CliFx.Tests.Utils;
+using CliFx.Tests.Utils.Extensions;
 using CliWrap;
 using CliWrap.Buffered;
 using FluentAssertions;
@@ -139,6 +140,53 @@ public class Command : ICommand
         stdErr.Trim().Should().Be("Hello world");
     }
 
+    [Fact]
+    public async Task Fake_console_can_read_key_presses()
+    {
+        // Arrange
+        var commandType = DynamicCommandBuilder.Compile(
+            // language=cs
+            @"
+[Command]
+public class Command : ICommand
+{   
+    public ValueTask ExecuteAsync(IConsole console)
+    {
+        console.Output.WriteLine(console.ReadKey().Key);
+        console.Output.WriteLine(console.ReadKey().Key);
+        console.Output.WriteLine(console.ReadKey().Key);
+
+        return default;
+    }
+}
+");
+
+        var application = new CliApplicationBuilder()
+            .AddCommand(commandType)
+            .UseConsole(FakeConsole)
+            .Build();
+
+        // Act
+        FakeConsole.EnqueueKey(new ConsoleKeyInfo('0', ConsoleKey.D0, false, false, false));
+        FakeConsole.EnqueueKey(new ConsoleKeyInfo('a', ConsoleKey.A, false, false, false));
+        FakeConsole.EnqueueKey(new ConsoleKeyInfo('\0', ConsoleKey.Backspace, false, false, false));
+
+        var exitCode = await application.RunAsync(
+            Array.Empty<string>(),
+            new Dictionary<string, string>()
+        );
+
+        var stdOut = FakeConsole.ReadOutputString();
+
+        // Assert
+        exitCode.Should().Be(0);
+        stdOut.Trim().Should().ConsistOfLines(
+            "D0",
+            "A",
+            "Backspace"
+        );
+    }
+
     [Fact]
     public void Console_does_not_emit_preamble_when_used_with_encoding_that_has_it()
     {

CliFx/Infrastructure/FakeConsole.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Concurrent;
 using System.IO;
 using System.Threading;
 
@@ -14,6 +15,7 @@ namespace CliFx.Infrastructure;
 public class FakeConsole : IConsole, IDisposable
 {
     private readonly CancellationTokenSource _cancellationTokenSource = new();
+    private readonly ConcurrentQueue<ConsoleKeyInfo> _keys = new();
 
     /// <inheritdoc />
     public ConsoleReader Input { get; }
@@ -91,9 +93,18 @@ public class FakeConsole : IConsole, IDisposable
     }
 
     /// <inheritdoc />
-    public void ReadKey(bool intercept = false)
-    {
-    }
+    public ConsoleKeyInfo ReadKey(bool intercept = false) =>
+        _keys.TryDequeue(out var key)
+            ? key
+            : throw new InvalidOperationException(
+                "Cannot read key because there are no key presses enqueued. " +
+                $"Use the `{nameof(EnqueueKey)}(...)` method to simulate a key press."
+            );
+
+    /// <summary>
+    /// Enqueues a simulated key press, which can then be read by calling <see cref="ReadKey"/>.
+    /// </summary>
+    public void EnqueueKey(ConsoleKeyInfo key) => _keys.Enqueue(key);
 
     /// <inheritdoc />
     public virtual void Dispose() => _cancellationTokenSource.Dispose();

CliFx/Infrastructure/IConsole.cs

@@ -91,7 +91,7 @@ public interface IConsole
     /// <summary>
     /// Obtains the next character or function key pressed by the user.
     /// </summary>
-    void ReadKey(bool intercept = false);
+    ConsoleKeyInfo ReadKey(bool intercept = false);
 }
 
 /// <summary>

CliFx/Infrastructure/SystemConsole.cs

@@ -94,7 +94,7 @@ public class SystemConsole : IConsole, IDisposable
     public void Clear() => Console.Clear();
 
     /// <inheritdoc />
-    public void ReadKey(bool intercept = false) => Console.ReadKey(intercept);
+    public ConsoleKeyInfo ReadKey(bool intercept = false) => Console.ReadKey(intercept);
 
     /// <inheritdoc />
     public void Dispose()