### Question:
EmptyTransactionCommitCohort extends AbstractTransactionCommitCohort { @Override public ListenableFuture<Void> commit() { complete(); return VOID_FUTURE; } EmptyTransactionCommitCohort(final AbstractClientHistory parent, final TransactionIdentifier txId); @Override ListenableFuture<Boolean> canCommit(); @Override ListenableFuture<Void> preCommit(); @Override ListenableFuture<Void> abort(); @Override ListenableFuture<Void> commit();  }### Answer:
@Test public void testCommit() throws Exception { final ListenableFuture<Void> commit = cohort.commit(); verify(history).onTransactionComplete(TRANSACTION_ID); Assert.assertNull(getWithTimeout(commit)); }