Fixes #3475. FakeConsole throws System.IndexOutOfRangeException using SetupFakeDriverAttribute.

Terminal.Gui/ConsoleDrivers/FakeDriver/FakeDriver.cs

@@ -40,6 +40,28 @@ public class FakeDriver : ConsoleDriver
     public static Behaviors FakeBehaviors = new ();
     public override bool SupportsTrueColor => false;
 
+    /// <inheritdoc />
+    public override int Cols
+    {
+        get => base.Cols;
+        internal set
+        {
+            base.Cols = value;
+            FakeConsole.SetBufferSize (Cols, Rows);
+        }
+    }
+
+    /// <inheritdoc />
+    public override int Rows
+    {
+        get => base.Rows;
+        internal set
+        {
+            base.Rows = value;
+            FakeConsole.SetBufferSize (Cols, Rows);
+        }
+    }
+
     public FakeDriver ()
     {
         Cols = FakeConsole.WindowWidth = FakeConsole.BufferWidth = FakeConsole.WIDTH;

UnitTests/TestHelpers.cs

@@ -171,6 +171,8 @@ public class SetupFakeDriverAttribute : BeforeAfterTestAttribute
         Debug.WriteLine ($"Before: {methodUnderTest.Name}");
         Assert.Null (Application.Driver);
         Application.Driver = new FakeDriver { Rows = 25, Cols = 25 };
+        Assert.Equal (FakeConsole.BufferWidth, Application.Driver.Cols);
+        Assert.Equal (FakeConsole.BufferHeight, Application.Driver.Rows);
         base.Before (methodUnderTest);
     }
 }