Fixes #4374 - Nukes all (?) legacy Driver and Application stuff; revamps tests (#4376)

Tests/UnitTests/FakeDriverBase.cs

@@ -0,0 +1,32 @@
+namespace UnitTests;
+
+/// <summary>
+///     Enables tests to create a FakeDriver for testing purposes.
+/// </summary>
+[Collection ("Global Test Setup")]
+public abstract class FakeDriverBase
+{
+    /// <summary>
+    ///     Creates a new FakeDriver instance with the specified buffer size.
+    ///     This is a convenience method for tests that need to use Draw() and DriverAssert
+    ///     without relying on Application.Driver.
+    /// </summary>
+    /// <param name="width">Width of the driver buffer</param>
+    /// <param name="height">Height of the driver buffer</param>
+    /// <returns>A configured IFakeDriver instance</returns>
+    protected static IDriver CreateFakeDriver (int width = 80, int height = 25)
+    {
+        var output = new FakeOutput ();
+
+        DriverImpl driver = new (
+                                                          new FakeInputProcessor (null),
+                                                          new OutputBufferImpl (),
+                                                          output,
+                                                          new AnsiRequestScheduler (new AnsiResponseParser ()),
+                                                          new SizeMonitorImpl (output));
+
+        driver.SetScreenSize (width, height);
+
+        return driver;
+    }
+}