message: [types] add unit tests for converting RequestItem and ResponseItem
  Add units tests for ensuring that when converting a proto to
  either a RequestItem or a ResponseItem that we won't panic.
diff: // Copyright (c) The Libra Core Contributors
  // SPDX-License-Identifier: Apache-2.0
  -use crate::get_with_proof::{
  +use crate::{
  + get_with_proof::{
  RequestItem, ResponseItem, UpdateToLatestLedgerRequest, UpdateToLatestLedgerResponse,
  + },
  + proto,
  };
  use proptest::prelude::*;
  -use proto_conv::test_helper::assert_protobuf_encode_decode;
  +use proto_conv::{test_helper::assert_protobuf_encode_decode, FromProto};
  proptest! {
  #[test]
  @@ -36,3 +39,19 @@ proptest! {
  assert_protobuf_encode_decode(&response);
  }
  }
  +
  +#[test]
  +fn request_item_is_none() {
  + let proto = proto::get_with_proof::RequestItem::default();
  +
  + let maybe_request_item = RequestItem::from_proto(proto);
  + assert!(maybe_request_item.is_err());
  +}
  +
  +#[test]
  +fn response_item_is_none() {
  + let proto = proto::get_with_proof::ResponseItem::default();
  +
  + let maybe_response_item = ResponseItem::from_proto(proto);
  + assert!(maybe_response_item.is_err());
  +}
  