@Test
  public void testLastBlockSeenHash() throws Exception {
    // Test the lastBlockSeenHash field works.

    // LastBlockSeenHash should be empty if never set.
    Wallet wallet = new Wallet(params);
    Protos.Wallet walletProto = new WalletProtobufSerializer().walletToProto(wallet);
    ByteString lastSeenBlockHash = walletProto.getLastSeenBlockHash();
    assertTrue(lastSeenBlockHash.isEmpty());

    // Create a block.
    Block block = params.getDefaultSerializer().makeBlock(BlockTest.blockBytes);
    Sha256Hash blockHash = block.getHash();
    wallet.setLastBlockSeenHash(blockHash);
    wallet.setLastBlockSeenHeight(1);

    // Roundtrip the wallet and check it has stored the blockHash.
    Wallet wallet1 = roundTrip(wallet);
    assertEquals(blockHash, wallet1.getLastBlockSeenHash());
    assertEquals(1, wallet1.getLastBlockSeenHeight());

    // Test the Satoshi genesis block (hash of all zeroes) is roundtripped ok.
    Block genesisBlock = MainNetParams.get().getGenesisBlock();
    wallet.setLastBlockSeenHash(genesisBlock.getHash());
    Wallet wallet2 = roundTrip(wallet);
    assertEquals(genesisBlock.getHash(), wallet2.getLastBlockSeenHash());
  }
  /**
   * Converts the given wallet to the object representation of the protocol buffers. This can be
   * modified, or additional data fields set, before serialization takes place.
   */
  public Protos.Wallet walletToProto(Wallet wallet) {
    Protos.Wallet.Builder walletBuilder = Protos.Wallet.newBuilder();
    walletBuilder.setNetworkIdentifier(wallet.getNetworkParameters().getId());
    if (wallet.getDescription() != null) {
      walletBuilder.setDescription(wallet.getDescription());
    }

    for (WalletTransaction wtx : wallet.getWalletTransactions()) {
      Protos.Transaction txProto = makeTxProto(wtx);
      walletBuilder.addTransaction(txProto);
    }

    walletBuilder.addAllKey(wallet.serializeKeychainToProtobuf());

    for (Script script : wallet.getWatchedScripts()) {
      Protos.Script protoScript =
          Protos.Script.newBuilder()
              .setProgram(ByteString.copyFrom(script.getProgram()))
              .setCreationTimestamp(script.getCreationTimeSeconds() * 1000)
              .build();

      walletBuilder.addWatchedScript(protoScript);
    }

    // Populate the lastSeenBlockHash field.
    Sha256Hash lastSeenBlockHash = wallet.getLastBlockSeenHash();
    if (lastSeenBlockHash != null) {
      walletBuilder.setLastSeenBlockHash(hashToByteString(lastSeenBlockHash));
      walletBuilder.setLastSeenBlockHeight(wallet.getLastBlockSeenHeight());
    }
    if (wallet.getLastBlockSeenTimeSecs() > 0)
      walletBuilder.setLastSeenBlockTimeSecs(wallet.getLastBlockSeenTimeSecs());

    // Populate the scrypt parameters.
    KeyCrypter keyCrypter = wallet.getKeyCrypter();
    if (keyCrypter == null) {
      // The wallet is unencrypted.
      walletBuilder.setEncryptionType(EncryptionType.UNENCRYPTED);
    } else {
      // The wallet is encrypted.
      walletBuilder.setEncryptionType(keyCrypter.getUnderstoodEncryptionType());
      if (keyCrypter instanceof KeyCrypterScrypt) {
        KeyCrypterScrypt keyCrypterScrypt = (KeyCrypterScrypt) keyCrypter;
        walletBuilder.setEncryptionParameters(keyCrypterScrypt.getScryptParameters());
      } else {
        // Some other form of encryption has been specified that we do not know how to persist.
        throw new RuntimeException(
            "The wallet has encryption of type '"
                + keyCrypter.getUnderstoodEncryptionType()
                + "' but this WalletProtobufSerializer does not know how to persist this.");
      }
    }

    if (wallet.getKeyRotationTime() != null) {
      long timeSecs = wallet.getKeyRotationTime().getTime() / 1000;
      walletBuilder.setKeyRotationTime(timeSecs);
    }

    populateExtensions(wallet, walletBuilder);

    for (Map.Entry<String, ByteString> entry : wallet.getTags().entrySet()) {
      Protos.Tag.Builder tag =
          Protos.Tag.newBuilder().setTag(entry.getKey()).setData(entry.getValue());
      walletBuilder.addTags(tag);
    }

    for (TransactionSigner signer : wallet.getTransactionSigners()) {
      // do not serialize LocalTransactionSigner as it's being added implicitly
      if (signer instanceof LocalTransactionSigner) continue;
      Protos.TransactionSigner.Builder protoSigner = Protos.TransactionSigner.newBuilder();
      protoSigner.setClassName(signer.getClass().getName());
      protoSigner.setData(ByteString.copyFrom(signer.serialize()));
      walletBuilder.addTransactionSigners(protoSigner);
    }

    walletBuilder.setSigsRequiredToSpend(wallet.getSigsRequiredToSpend());

    // Populate the wallet version.
    walletBuilder.setVersion(wallet.getVersion());

    return walletBuilder.build();
  }