### Question:
TransactionSet { public List<Transaction> getTransactionsWithSender(UscAddress senderAddress) { List<Transaction> list = this.transactionsByAddress.get(senderAddress); if (list == null) { return new ArrayList<>(); } return list; } TransactionSet();  TransactionSet(TransactionSet transactionSet);  TransactionSet(Map<Keccak256, Transaction> transactionsByHash, Map<UscAddress, List<Transaction>> transactionsByAddress); void addTransaction(Transaction transaction); boolean hasTransaction(Transaction transaction); void removeTransactionByHash(Keccak256 hash); List<Transaction> getTransactions(); List<Transaction> getTransactionsWithSender(UscAddress senderAddress);  }### Answer:
@Test public void getEmptyTransactionListByUnknownSender() { TransactionSet txset = new TransactionSet(); List<Transaction> result = txset.getTransactionsWithSender(new UscAddress(new byte[20])); Assert.assertNotNull(result); Assert.assertTrue(result.isEmpty()); }