QueueBufferEdit.cs

            // On a background thread, perform our typing work.
            ThreadPool.QueueUserWorkItem((state) =>
            {
                Random random = new Random();

                for (int i = 0; i < _textToType.Length; i++)
                {
                    // Dispatch back to the UI thread to make the edit on the buffer
                    _dispatcher.Invoke(new Action(() => 
                    {
                        ITextSnapshot snapshot = _insertionPoint.TextBuffer.CurrentSnapshot;
                        SnapshotPoint insertionPoint = _insertionPoint.GetPoint(snapshot);

                        if (i == 0)
                            CaptureInsertionSpan(insertionPoint);

                        snapshot.TextBuffer.Insert(insertionPoint, _textToType.Substring(i, 1));

                    }), DispatcherPriority.Normal);

                    // Between each typing action, sleep for a little while
                    Thread.Sleep(50 + random.Next(200));
                }
            });