public void UndoInsertion()
{
var textBuffer = new TextBuffer("", MockFor<IContentType>().Object);
var undoServiceFactory = new UndoServiceFactory();
var undoService = undoServiceFactory.ForTextBuffer(textBuffer);
var oldSnapshot = textBuffer.CurrentSnapshot;
textBuffer.Insert(0, "text");
var changes = new List<TextChangeArgs>();
textBuffer.Changed += (sender, args) => changes.Add(args);
undoService.Undo();
Assert.AreEqual(1, changes.Count);
Assert.AreSame(oldSnapshot, textBuffer.CurrentSnapshot);
}