TestableTextBox.cs

 using System; 
 using System.Windows.Forms; 
 namespace Notepad 
 { 
 /// <summary> 
 /// Dummy class allowing use of the ITestTextBox interface in testing. 
 ///   (See TestScroll.cs and MockTextBox.cs) 
 /// </summary> 
 class TestableTextBox: TextBox, ITestTextBox { 
 } 
 }