public void UndoTest ()
{
MaskedTextBox mtb;
mtb = new MaskedTextBox ();
mtb.Text = "abcdef";
Assert.AreEqual (false, mtb.CanUndo, "#A0-c");
mtb.Undo ();
Assert.AreEqual ("abcdef", mtb.Text, "#A1");
Assert.AreEqual (false, mtb.CanUndo, "#A1-c");
mtb.Text = "cdef";
mtb.ClearUndo ();
Assert.AreEqual ("cdef", mtb.Text, "#A2");
Assert.AreEqual (false, mtb.CanUndo, "#A2-c");
mtb.Dispose ();
}