public static void refreshSuperUserGroupsConfiguration() {
    //load server side configuration;
    refreshSuperUserGroupsConfiguration(new Configuration());
  }
@Test
   public void testProxyUsersWithProviderOverride() throws Exception {
     Configuration conf = new Configuration();
     conf.set(
         CommonConfigurationKeysPublic.HADOOP_SECURITY_IMPERSONATION_PROVIDER_CLASS,
         "org.apache.hadoop.security.authorize.TestProxyUsers$TestDummyImpersonationProvider");
     ProxyUsers.refreshSuperUserGroupsConfiguration(conf);
 
     // First try proxying a group that's allowed
     UserGroupInformation realUserUgi = UserGroupInformation
     .createUserForTesting(REAL_USER_NAME, SUDO_GROUP_NAMES);
     UserGroupInformation proxyUserUgi = UserGroupInformation.createProxyUserForTesting(
         PROXY_USER_NAME, realUserUgi, GROUP_NAMES);
 
     // From good IP
     assertAuthorized(proxyUserUgi, "1.2.3.4");
     // From bad IP
     assertAuthorized(proxyUserUgi, "1.2.3.5");
 
     // Now try proxying a group that's not allowed
     realUserUgi = UserGroupInformation
     .createUserForTesting(REAL_USER_NAME, GROUP_NAMES);
     proxyUserUgi = UserGroupInformation.createProxyUserForTesting(
         PROXY_USER_NAME, realUserUgi, GROUP_NAMES);
 
     // From good IP
     assertNotAuthorized(proxyUserUgi, "1.2.3.4");
     // From bad IP
     assertNotAuthorized(proxyUserUgi, "1.2.3.5");
   }