@Override
    public void postOpen(ObserverContext<? extends RegionCoprocessorEnvironment> c) {
      RegionCoprocessorEnvironment env = c.getEnvironment();
      Configuration conf = env.getConfiguration();
      sleepTime.set(conf.getLong(SLEEP_TIME_CONF_KEY, DEFAULT_SLEEP_TIME));
    }
This copro sleeps 20 second. The first call it fails. The second time, it works.
hbase-server/src/test/java/org/apache/hadoop/hbase/client/AbstractTestCITimeout.java