Added unit tests

Author: tig

Terminal.Gui/Application/Application.Run.cs

@@ -508,6 +508,7 @@ public static void LayoutAndDraw (bool forceDraw = false)
         if (ClearScreenNextIteration)
         {
             forceDraw = true;
+            ClearScreenNextIteration = false;
         }
         if (forceDraw)
         {

UnitTests/Application/ApplicationScreenTests.cs

@@ -0,0 +1,67 @@
+using Xunit.Abstractions;
+
+namespace Terminal.Gui.ApplicationTests.NavigationTests;
+
+public class ApplicationScreenTests (ITestOutputHelper output)
+{
+    [Fact]
+    public void ClearScreenNextIteration_Resets_To_False_After_LayoutAndDraw ()
+    {
+        // Arrange
+        Application.Init ();
+
+        // Act
+        Application.ClearScreenNextIteration = true;
+        Application.LayoutAndDraw ();
+
+        // Assert
+        Assert.False (Application.ClearScreenNextIteration);
+
+        // Cleanup
+        Application.ResetState (true);
+    }
+
+    [Fact]
+    [SetupFakeDriver]
+    public void ClearContents_Called_When_Top_Frame_Changes ()
+    {
+        // Arrange
+        Application.Init ();
+        Application.Top = new Toplevel ();
+        Application.TopLevels.Push (Application.Top);
+
+        int clearedContentsRaised = 0;
+
+        Application.Driver!.ClearedContents += (e, a) => clearedContentsRaised++;
+
+        // Act
+        Application.LayoutAndDraw ();
+
+        // Assert
+        Assert.Equal (0, clearedContentsRaised);
+
+        // Act
+        Application.Top.SetNeedsLayout ();
+        Application.LayoutAndDraw ();
+
+        // Assert
+        Assert.Equal (0, clearedContentsRaised);
+
+        // Act
+        Application.Top.X = 1;
+        Application.LayoutAndDraw ();
+
+        // Assert
+        Assert.Equal (1, clearedContentsRaised);
+
+        // Act
+        Application.Top.Width = 10;
+        Application.LayoutAndDraw ();
+
+        // Assert
+        Assert.Equal (2, clearedContentsRaised);
+
+        // Cleanup
+        Application.ResetState (true);
+    }
+}