def METHOD_NAME(self):
    """
    verify that write buffering is on.
    """
    f = LoopbackFile("r+", 1)
    f.write(b"Complete line.\nIncomplete line.")
    self.assertEqual(f.readline(), "Complete line.\n")
    self.assertEqual(f.readline(), "")
    f.write("..\n")
    self.assertEqual(f.readline(), "Incomplete line...\n")
    f.close()