public static void refreshSuperUserGroupsConfiguration() {
    //load server side configuration;
    refreshSuperUserGroupsConfiguration(new Configuration());
  }
@Test
  public void testNoHostsForUsers() throws Exception {
    Configuration conf = new Configuration(false);
    conf.set("y." + REAL_USER_NAME + ".users",
      StringUtils.join(",", Arrays.asList(AUTHORIZED_PROXY_USER_NAME)));
    ProxyUsers.refreshSuperUserGroupsConfiguration(conf, "y");

    UserGroupInformation realUserUgi = UserGroupInformation
      .createRemoteUser(REAL_USER_NAME);
    UserGroupInformation proxyUserUgi = UserGroupInformation.createProxyUserForTesting(
      AUTHORIZED_PROXY_USER_NAME, realUserUgi, GROUP_NAMES);

    // IP doesn't matter
    assertNotAuthorized(proxyUserUgi, "1.2.3.4");
  }