code: public static SimpleRequest makeRequest(Messages.PayloadType payloadType, int reqLength,
                                            int respLength) {
      ByteString body = ByteString.copyFrom(new byte[reqLength]);
      Payload payload = Payload.newBuilder()
          .setType(payloadType)
          .setBody(body)
          .build();
  
      return SimpleRequest.newBuilder()
          .setResponseType(payloadType)
          .setResponseSize(respLength)
          .setPayload(payload)
          .build();
    }
docs: Construct a {@link SimpleRequest} with the specified dimensions.