Investigate fluent assertions for testing v2

TerminalGuiFluentAssertions/Class1.cs

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+using System.Collections.Concurrent;
+using System.Drawing;
+using Terminal.Gui;
+
+namespace TerminalGuiFluentAssertions;
+
+class FakeInput<T> : IConsoleInput<T>
+{
+    /// <inheritdoc />
+    public void Dispose () { }
+
+    /// <inheritdoc />
+    public void Initialize (ConcurrentQueue<T> inputBuffer) { }
+
+    /// <inheritdoc />
+    public void Run (CancellationToken token)
+    {
+        // Simulate an infinite loop that checks for cancellation
+        token.WaitHandle.WaitOne (); // Blocks until the token is cancelled
+    }
+}
+
+class FakeNetInput : FakeInput<ConsoleKeyInfo>, INetInput
+{
+
+}
+
+class FakeWindowsInput : FakeInput<WindowsConsole.InputRecord>, IWindowsInput
+{
+
+}
+
+class FakeOutput : IConsoleOutput
+{
+    public Size Size { get; set; }
+
+    /// <inheritdoc />
+    public void Dispose ()
+    {
+
+    }
+
+    /// <inheritdoc />
+    public void Write (ReadOnlySpan<char> text)
+    {
+
+    }
+
+    /// <inheritdoc />
+    public void Write (IOutputBuffer buffer)
+    {
+
+    }
+
+    /// <inheritdoc />
+    public Size GetWindowSize ()
+    {
+        return Size;
+    }
+
+    /// <inheritdoc />
+    public void SetCursorVisibility (CursorVisibility visibility)
+    {
+
+    }
+
+    /// <inheritdoc />
+    public void SetCursorPosition (int col, int row)
+    {
+
+    }
+
+}
+/// <summary>
+/// Entry point to fluent assertions.
+/// </summary>
+public static class With
+{
+    /// <summary>
+    /// Entrypoint to fluent assertions
+    /// </summary>
+    /// <param name="width"></param>
+    /// <param name="height"></param>
+    /// <returns></returns>
+    public static GuiTestContext<T> A<T> (int width, int height) where T : Toplevel, new ()
+    {
+        return new GuiTestContext<T> (width,height);
+    }
+}
+public class GuiTestContext<T> where T : Toplevel, new()
+{
+    private readonly CancellationTokenSource _cts;
+    private readonly Task _runTask;
+
+    internal GuiTestContext (int width, int height)
+    {
+        IApplication origApp = ApplicationImpl.Instance;
+
+        var netInput = new FakeNetInput ();
+        var winInput = new FakeWindowsInput ();
+        var output = new FakeOutput ();
+
+        output.Size = new (width, height);
+
+        var v2 = new ApplicationV2(
+                                    () => netInput,
+                                    ()=>output,
+                                    () => winInput,
+                                    () => output);
+
+        // Create a cancellation token
+        _cts = new ();
+
+        // Start the application in a background thread
+        _runTask = Task.Run (() =>
+                             {
+                                 try
+                                 {
+                                     ApplicationImpl.ChangeInstance (v2);
+
+                                     v2.Init ();
+
+                                     Application.Run<T> (); // This will block, but it's on a background thread now
+
+                                     Application.Shutdown ();
+                                 }
+                                 catch (OperationCanceledException)
+                                 {
+
+                                 }
+                                 finally
+                                 {
+                                     ApplicationImpl.ChangeInstance (origApp);
+                                 }
+                             }, _cts.Token);
+
+        Application.Shutdown ();
+    }
+
+    /// <summary>
+    /// Stops the application and waits for the background thread to exit.
+    /// </summary>
+    public void Stop ()
+    {
+        _cts.Cancel ();
+        Application.Invoke (()=>Application.RequestStop());
+        _runTask.Wait (); // Ensure the background thread exits
+    }
+
+    // Cleanup to avoid state bleed between tests
+    public void Dispose ()
+    {
+    }
+}
+