Addind more Unit Test

Shapes/Rectangle.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Drawing;
 using System.Drawing.Imaging;
 using System.IO;
@@ -112,6 +113,7 @@ namespace Shapes
 
         public override void Scale(double scaleFactor)
         {
+            Validator.ValidatePositiveDouble(scaleFactor, "Invalid scale factor");
             foreach (var point in Points)
             {
                 point.X *= scaleFactor;
@@ -124,6 +126,7 @@ namespace Shapes
             _fileWriter.SaveShape(stream, this);
         }
 
+        [ExcludeFromCodeCoverage]
         public override void Draw(Stream stream)
         {
             var tmp = new Bitmap((int) Width * 2, (int) Height * 2);