@Before
  public void setUp() throws Exception {
    clientConf = new Configuration(TEST_UTIL.getConfiguration());
    clientConf.setClass(RpcClientFactory.CUSTOM_RPC_CLIENT_IMPL_CONF_KEY, rpcClientImpl,
      RpcClient.class);
    String serverPrincipalConfigName = "hbase.test.multiple.principal.first";
    String serverPrincipalConfigName2 = "hbase.test.multiple.principal.second";
    clientConf.set(serverPrincipalConfigName, SERVER_PRINCIPAL);
    clientConf.set(serverPrincipalConfigName2, SERVER_PRINCIPAL2);
    serverConf = new Configuration(TEST_UTIL.getConfiguration());
    serverConf.setClass(RpcServerFactory.CUSTOM_RPC_SERVER_IMPL_CONF_KEY, rpcServerImpl,
      RpcServer.class);
    SecurityInfo securityInfo = new SecurityInfo(Kind.HBASE_AUTH_TOKEN, serverPrincipalConfigName2,
      serverPrincipalConfigName);
    SecurityInfo.addInfo(TestProtobufRpcProto.getDescriptor().getName(), securityInfo);

    UserGroupInformation.setConfiguration(clientConf);
    clientUGI = UserGroupInformation.loginUserFromKeytabAndReturnUGI(CLIENT_PRINCIPAL,
      KEYTAB_FILE.getCanonicalPath());
    loginAndStartRpcServer(SERVER_PRINCIPAL, 0);
    rpcClient = clientUGI.doAs((PrivilegedExceptionAction<RpcClient>) () -> RpcClientFactory
      .createClient(clientConf, HConstants.DEFAULT_CLUSTER_ID.toString()));
  }
Tests for HBASE-28321, where we have multiple server principals candidates for a rpc service.
<p>
Put here just because we need to visit some package private classes under this package.
hbase-server/src/test/java/org/apache/hadoop/hbase/ipc/TestMultipleServerPrincipalsIPC.java