@Override
  public List<PrivilegedOperation> bootstrap(Configuration configuration)
      throws ResourceHandlerException {
    // if bootstrap is called on this class, disk is already enabled
    // so no need to check again
    this.cGroupsHandler
      .initializeCGroupController(CGroupsHandler.CGroupController.BLKIO);
    return null;
  }
@Test
  public void testBootstrap() throws Exception {
    Configuration conf = new YarnConfiguration();
    List<PrivilegedOperation> ret =
        cGroupsBlkioResourceHandlerImpl.bootstrap(conf);
    verify(mockCGroupsHandler, times(1)).initializeCGroupController(
        CGroupsHandler.CGroupController.BLKIO);
    Assert.assertNull(ret);
  }