@Test
  public void testNoCodec() throws IOException, ServiceException {
    Configuration clientConf = new Configuration(CONF);
    RpcServer rpcServer = createRpcServer("testRpcServer",
      Lists.newArrayList(new RpcServer.BlockingServiceAndInterface(SERVICE, null)),
      new InetSocketAddress("localhost", 0), CONF, new FifoRpcScheduler(CONF, 1));
    try (AbstractRpcClient<?> client = createRpcClientNoCodec(clientConf)) {
      rpcServer.start();
      BlockingInterface stub = newBlockingStub(client, rpcServer.getListenerAddress());
      HBaseRpcController pcrc = new HBaseRpcControllerImpl();
      String message = "hello";
      assertEquals(message,
        stub.echo(pcrc, EchoRequestProto.newBuilder().setMessage(message).build()).getMessage());
      assertNull(pcrc.cellScanner());
    } finally {
      rpcServer.stop();
    }
  }
Ensure we do not HAVE TO HAVE a codec.
hbase-server/src/test/java/org/apache/hadoop/hbase/ipc/AbstractTestIPC.java