doReturn("rootShard").when(rootShard).toString();
doReturn(producerMock).when(rootShard).createProducer(any(Collection.class));
doReturn(shardTxMock).when(producerMock).createTransaction();
+ doNothing().when(producerMock).close();
doNothing().when(shardTxMock).ready();
doReturn(Futures.immediateFuture(null)).when(shardTxMock).submit();