TransactionsPool { public boolean checkExists(String transactionHash) { Util.check(transactionHash != null, "transaction != null"); synchronized (locker) { return (checkExistsNoLock(transactionHash)); } }  List<String> getTransactions(); boolean addTransaction(String transactionHash); boolean checkExists(String transactionHash); void addBlock(Block block);  }
@Test(expected = IllegalArgumentException.class) public void testCheckShouldThrowException() { TransactionsPool transactionsProcessed = new TransactionsPool(); transactionsProcessed.checkExists(null); }