public void TestTransactFail()
        {
            SharedMemoryStream shared = new SharedMemoryStream();

            FragmentedFile.CreateNew(shared, 512, 100, 2).Dispose();

            using (FragmentedFile ff = new FragmentedFile(shared, 512, 100, 2))
            {
                long   id;
                byte[] bytes = MakeBytes(255);
                using (Stream write = ff.Create(out id))
                    using (ITransactable trans = (ITransactable)write)
                    {
                        write.Write(bytes, 0, bytes.Length);
                        ff.Dispose();
                        trans.Commit();
                    }
            }
        }