Add text prompt support

src/Spectre.Console.Tests/Tools/TestableAnsiConsole.cs

@@ -0,0 +1,55 @@
+using System;
+using System.IO;
+using System.Text;
+using Spectre.Console.Rendering;
+using Spectre.Console.Tests.Tools;
+
+namespace Spectre.Console.Tests
+{
+    public sealed class TestableAnsiConsole : IDisposable, IAnsiConsole
+    {
+        private readonly StringWriter _writer;
+        private readonly IAnsiConsole _console;
+
+        public string Output => _writer.ToString();
+
+        public Capabilities Capabilities => _console.Capabilities;
+        public Encoding Encoding => _console.Encoding;
+        public int Width { get; }
+        public int Height => _console.Height;
+        public IAnsiConsoleCursor Cursor => _console.Cursor;
+        public TestableConsoleInput Input { get; }
+
+        IAnsiConsoleInput IAnsiConsole.Input => Input;
+
+        public TestableAnsiConsole(ColorSystem system, AnsiSupport ansi = AnsiSupport.Yes, int width = 80)
+        {
+            _writer = new StringWriter();
+            _console = AnsiConsole.Create(new AnsiConsoleSettings
+            {
+                Ansi = ansi,
+                ColorSystem = (ColorSystemSupport)system,
+                Out = _writer,
+                LinkIdentityGenerator = new TestLinkIdentityGenerator(),
+            });
+
+            Width = width;
+            Input = new TestableConsoleInput();
+        }
+
+        public void Dispose()
+        {
+            _writer?.Dispose();
+        }
+
+        public void Clear(bool home)
+        {
+            _console.Clear(home);
+        }
+
+        public void Write(Segment segment)
+        {
+            _console.Write(segment);
+        }
+    }
+}