### Question:
TransactionNodeInformation { @Nonnull public Set<NodeID> getNodesByTransaction(@Nonnull final Keccak256 transactionHash) { Set<NodeID> result = nodesByTransaction.get(transactionHash); if (result == null) { result = new HashSet<>(); } return Collections.unmodifiableSet(result); } TransactionNodeInformation(final int maxTransactions, final int maxPeers);  TransactionNodeInformation(); void addTransactionToNode(@Nonnull final Keccak256 transactionHash, @Nonnull final NodeID nodeID); @Nonnull Set<NodeID> getNodesByTransaction(@Nonnull final Keccak256 transactionHash);  }### Answer:
@Test public void getIsEmptyIfNotPresent() { final TransactionNodeInformation nodeInformation = new TransactionNodeInformation(); Assert.assertTrue(nodeInformation.getNodesByTransaction(createBlockHash(0)).isEmpty()); }