@Test
public void retry_confirmable_message() throws InterruptedException {

    CoapMessage msg = new CoapMessage(1, MessageType.CONFIRMABLE, 1, 1234, null, null, null);
    WriteRequest writeRequest = new DefaultWriteRequest(msg);
    filter.messageWriting(session, writeRequest, writeController);
    // verify
    // wait more than the first timeout
    Thread.sleep(3500L);
    // first write
    verify(writeController).callWriteNextFilter(writeRequest);
    // retry
    session.write(msg);
}