@Test(timeout = 60000)
public void testDelaySendingAckToUpstream() throws Exception {

  final MetricsDataNodeFaultInjector mdnFaultInjector =
      new MetricsDataNodeFaultInjector() {
        @Override
        public void delaySendingAckToUpstream(final String upstreamAddr)
            throws IOException {
          delayOnce();
        }
        @Override
        public void logDelaySendingAckToUpstream(final String upstreamAddr,
            final long delayMs) throws IOException {
          logDelay(delayMs);
        }
      };
  verifyFaultInjectionDelayPipeline(mdnFaultInjector);
}