@Test
  public void testInstallShutdownHook() throws IOException {
    // Test for HBASE-26951
    assertTrue(HTU.getHBaseCluster().getRegionServer(0).isShutdownHookInstalled());
  }
Tests an on-the-fly RPC that was scheduled for the earlier RS on the same port for openRegion.
The region server should reject this RPC. (HBASE-9721)
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestRegionServerNoMaster.java