public void testAddDuplicateElement_withinTxn() throws Exception {
final String element = "item1";
final String setName = randomString();
final TransactionContext context = client.newTransactionContext();
context.beginTransaction();
final TransactionalSet<Object> txnSet = context.getSet(setName);
assertTrue(txnSet.add(element));
assertFalse(txnSet.add(element));
context.commitTransaction();