example custom password generation

FixturesLoader.php

<?php
    public function encodePassword(User $user, $plainPassword)
    {
        /** @var \Symfony\Component\Security\Core\Encoder\PasswordEncoderInterface $encoder */
        $encoder = $this->container->get('security.encoder_factory')
            ->getEncoder($user);

        return $encoder->encodePassword($plainPassword, $user->getSalt());
    }