@Override
    public Matcher visit(IsNull isNull) {
      return isNull
          .getField()
          .accept(
              new VisitorAdapter<Matcher>() {

                @Override
                public Matcher visit(final Field field) {
                  return new Matcher() {

                    @Override
                    public boolean match(DataRecord record) {
                      return record.get(field.getFieldMetadata()) == null;
                    }
                  };
                }

                @Override
                public Matcher visit(StagingBlockKey stagingBlockKey) {
                  return new Matcher() {

                    @Override
                    public boolean match(DataRecord record) {
                      return record
                              .getRecordMetadata()
                              .getRecordProperties()
                              .get(StagingStorage.METADATA_STAGING_BLOCK_KEY)
                          == null;
                    }
                  };
                }
              });
    }
    @Test
    public void addressConstantIsConsistentWithNemesisBlock() {
      // Arrange:
      final Block block = this.loadNemesisBlock();
      final Address blockAddress = block.getSigner().getAddress();

      // Assert:
      Assert.assertThat(blockAddress, IsEqual.equalTo(NEMESIS_BLOCK_INFO.getAddress()));
      Assert.assertThat(
          blockAddress.getPublicKey(),
          IsEqual.equalTo(NEMESIS_BLOCK_INFO.getAddress().getPublicKey()));
      Assert.assertThat(blockAddress.getPublicKey(), IsNull.notNullValue());
    }
    @Test
    public void nemesisTransactionSignersHavePublicKeys() {
      // Arrange:
      final Block block = this.loadNemesisBlock();

      // Act:
      final Set<Address> signerAddresses =
          block
              .getTransactions()
              .stream()
              .map(t -> t.getSigner().getAddress())
              .collect(Collectors.toSet());

      // Assert:
      for (final Address address : signerAddresses) {
        Assert.assertThat(address.getPublicKey(), IsNull.notNullValue());
      }
    }
    @Test
    public void nemesisBlockCanBeCreated() {
      // Act:
      final Block block = this.loadNemesisBlock();

      // Assert:
      Assert.assertThat(
          block.getSigner().getAddress(), IsEqual.equalTo(NEMESIS_BLOCK_INFO.getAddress()));
      Assert.assertThat(block.getType(), IsEqual.equalTo(-1));
      Assert.assertThat(block.getVersion(), IsEqual.equalTo(EXPECTED_VERSION));
      Assert.assertThat(block.getTimeStamp(), IsEqual.equalTo(TimeInstant.ZERO));

      // 2 multisig aggregate transactions
      Assert.assertThat(
          block.getTotalFee(), IsEqual.equalTo(EXPECTED_MULTISIG_AGGREGATE_FEE.multiply(2)));
      Assert.assertThat(block.getPreviousBlockHash(), IsEqual.equalTo(Hash.ZERO));
      Assert.assertThat(block.getHeight(), IsEqual.equalTo(BlockHeight.ONE));
      Assert.assertThat(block.getTransactions().size(), IsEqual.equalTo(NUM_NEMESIS_TRANSACTIONS));

      Assert.assertThat(block.getDifficulty(), IsEqual.equalTo(BlockDifficulty.INITIAL_DIFFICULTY));
      Assert.assertThat(block.getGenerationHash(), IsNull.notNullValue());
    }