Unit test problem with addUser

UserRepository

class UserRepository implements UserProviderInterface
{
/**
     * Add a user to the database
     *
     * @param User $user
     * @return User
     */
    public function addUser(User $user)
    {
        $pbnlAccount = $this->userToEntities($user);

        if(!$this->doesUserExist($user)) {
            $pbnlAccount->setUidNumber($this->getNewUidNumber());
            $this->ldapEntityManager->persist($pbnlAccount);
            $this->ldapEntityManager->flush();
        }
        else {
            throw new UserAlreadyExistException("The user ".$user->getUid()." already exists.");
        }

        return $this->getUserByUid($user->getUid());
    }

    /**
     * Checks if this user already exists
     * For this the function uses the uid and the uidNumber
     * @param $user
     * @return bool
     * @throws UserNotUniqueException if there are more than one users with the same uid or uidNumber
     */
    private function doesUserExist(User $user)
    {
        $ldapUserRepo = $this->ldapEntityManager->getRepository(PbnlAccount::class);

        $users = $ldapUserRepo->findByUid($user->getUid());
        if(count($users) == 1) return true;
        if(count($users) > 1) throw new UserNotUniqueException("The user with the uid ".$user->getUid()." is not unique!");

        $users = $ldapUserRepo->findByUidNumber($user->getUidNumber());
        if(count($users) == 1) return true;
        if(count($users) > 1) throw new UserNotUniqueException("The user with the uid ".$user->getUid()." is not unique!");;

        return false;
    }

    /**
     * Creates a PbnlAccount with the data of an User object
     *
     * @param $user
     * @return PbnlAccount
     */
    private function userToEntities(User $user)
    {
        $pbnlAccount = new PbnlAccount();
        $pbnlAccount->setL($user->getCity());
        $pbnlAccount->setOu($user->getStamm());
        $pbnlAccount->setStreet($user->getStreet());
        $pbnlAccount->setPostalCode($user->getPostalCode());
        $pbnlAccount->setGivenName($user->getGivenName());
        $pbnlAccount->setUid($user->getUid());
        $pbnlAccount->setCn($user->getFirstName());
        $pbnlAccount->setSn($user->getLastName());
        $pbnlAccount->setMail($user->getMail());
        $pbnlAccount->setTelephoneNumber($user->getHomePhoneNumber());
        $pbnlAccount->setMobile($user->getMobilePhoneNumber());
        $pbnlAccount->setGidNumber("501");
        $pbnlAccount->setHomeDirectory("/home/".$user->getUid());
        $pbnlAccount->setUidNumber($user->getUidNumber());
        $pbnlAccount->setObjectClass(["inetOrgPerson","posixAccount","pbnlAccount"]);

        return $pbnlAccount;
    }

    /**
     * Returns the next uidNumber
     * Its the highest uidNumber of the pbnlAccounts + 1
     * @return int
     */
    private function getNewUidNumber()
    {
        /** @var  $users User[]*/
        $users = $this->ldapEntityManager->getRepository(PbnlAccount::class)->findAll();
        $highesUidNumber = 0;
        foreach ($users as $user) {
            if($user->getUidNumber() > $highesUidNumber) {
                $highesUidNumber = $user->getUidNumber();
            }
        }
        return $highesUidNumber + 1;
    }
    
    /**
     * Searches the PbnlAccount (ldap) and returns a User
     * Find by GivenName
     *
     * @param string $givenName
     * @return User
     */
    public function getUserByUid(String $givenName)
    {
        /** @var Repository $pbnlAccountRepository */
        $pbnlAccountRepository = $this->ldapEntityManager->getRepository(PbnlAccount::class);

        /** @var PbnlAccount $ldapPbnlAccount[] */
        $ldapPbnlAccount = $pbnlAccountRepository->findOneByUid($givenName);

        if (count($ldapPbnlAccount) == 0) {
            throw new UsernameNotFoundException(
                sprintf('Uid "%s" does not exist.', $givenName)
            );
        }

        return $this->entitiesToUser($ldapPbnlAccount);
    }
}