test.php

<?php

class BalanceTransaction
{
    public function __construct(User $user, $amount, $reason)
    {
        $this->updateReason($reason);
    }

    protected function updateReason($reason)
    {
        $this->reason = new TransactionReason($this, $reason);
    }
}

class BalanceTransactionRepository extends ServiceEntityRepository
{
    public function __construct(ManagerRegistry $registry)
    {
        parent::__construrct($registry, BalanceTransaction::class);
    }

    public function add(BalanceTransaction $transaction)
    {
        $this->em->persist($transaction);
        $this->em->flush();
    }
}

class AddTransaction interface AddTransactionInterface
{
    private $transactions;

    private $dispatcher;

    private $validator;

    public function __construct(BalanceTransactionRepository $transactions, ValidatorInterface $validator, EventDispatcherInterface $dispatcher)
    {
        $this->transactions = $transactions;

        $this->logger = new NullLogger();
        $this->dispatcher = $dispatcher;
        $this->validator = $validator;
    }

    public function setLogger(LoggerInterface $logger)
    {
        $this->logger = $logger;
    }

    public function add(UserInterface $user, $amount, $reason)
    {
        $transaction = new BalanceTransaction($user, $amount, $reason);

        $errors = $this->validator->validate($transaction);

        if (count($errors) > 0) {
            throw new Exception('');
        }

        $this->transactions->add($transaction);

        $this->dispatcher->dispatch('transaction_added', new Event($transaction));
    }
}

class TransactionalAddTransaction implements AddTransactionInterface
{
    private $conneciton;

    private $handler;

    public function __construct(Connection $conneciton, AddTransaction $handler)
    {
        $this->conneciton = $conneciton;
        $this->handler = $handler;
    }

    public function add(UserInterface $user, $amount)
    {
        $this->connection->beginTransaction();

        try {
            $this->handler->add($user, $amount);
            $this->connection->commit();
        } catch (\Exception $exception) {
            $this->connection->rollback();
        }
    }
}