public static void refreshSuperUserGroupsConfiguration() {
    //load server side configuration;
    refreshSuperUserGroupsConfiguration(new Configuration());
  }
@Test
  public void testWildcardUser() {
    Configuration conf = new Configuration();
    conf.set(
      DefaultImpersonationProvider.getTestProvider().
          getProxySuperuserUserConfKey(REAL_USER_NAME),
      "*");
    conf.set(
      DefaultImpersonationProvider.getTestProvider().
          getProxySuperuserIpConfKey(REAL_USER_NAME),
      PROXY_IP);
    ProxyUsers.refreshSuperUserGroupsConfiguration(conf);

    // First try proxying a user that's allowed
    UserGroupInformation realUserUgi = UserGroupInformation
        .createRemoteUser(REAL_USER_NAME);
    UserGroupInformation proxyUserUgi = UserGroupInformation.createProxyUserForTesting(
        AUTHORIZED_PROXY_USER_NAME, realUserUgi, GROUP_NAMES);

    // From good IP
    assertAuthorized(proxyUserUgi, "1.2.3.4");
    // From bad IP
    assertNotAuthorized(proxyUserUgi, "1.2.3.5");

    // Now try proxying a different user (just to make sure we aren't getting spill over
    // from the other test case!)
    realUserUgi = UserGroupInformation.createRemoteUser(REAL_USER_NAME);
    proxyUserUgi = UserGroupInformation.createProxyUserForTesting(
        PROXY_USER_NAME, realUserUgi, OTHER_GROUP_NAMES);
    
    // From good IP
    assertAuthorized(proxyUserUgi, "1.2.3.4");
    // From bad IP
    assertNotAuthorized(proxyUserUgi, "1.2.3.5");
  }