code: @Test public void testHeartBeat() throws Exception {
    url=url.addParameter(Constants.DUBBO_VERSION_KEY,"2.1.1");
    channel.setAttribute(HeaderExchangeHandler.KEY_READ_TIMESTAMP,System.currentTimeMillis());
    channel.setAttribute(HeaderExchangeHandler.KEY_WRITE_TIMESTAMP,System.currentTimeMillis());
    Thread.sleep(2000L);
    task.run();
    List<Object> objects=channel.getSentObjects();
    Assert.assertTrue(objects.size() > 0);
    Object obj=objects.get(0);
    Assert.assertTrue(obj instanceof Request);
    Request request=(Request)obj;
    Assert.assertTrue(request.isHeartbeat());
  }
  