Making domain services testable

OfferNumberGenerator.php

<?php

namespace Sps\Intranet\Domain\Model\Offer;

use Sps\Intranet\Domain\Model\Partner\PartnerId;
use Sps\Intranet\Infrastructure\Projection\Mongo\OfferReadModelFinder;

/**
 * Class OfferNumberGenerator
 * @package Sps\Intranet\Domain\Model\Offer
 */
class OfferNumberGenerator
{
    /** @var OfferReadModelFinder $offers */
    private $offers;

    /**
     * OfferNumberGenerator constructor.
     * @param OfferReadModelFinder $offers
     */
    public function __construct(OfferReadModelFinder $offers)
    {
        $this->offers = $offers;
    }

    /**
     * @param PartnerId $partnerId
     * @return OfferNumber
     */
    function generate(PartnerId $partnerId)
    {
        $currentOfferNumber = $this->offers->currentOfferNumber($partnerId);

        return null !== $currentOfferNumber ? $currentOfferNumber->next() : OfferNumber::generate();
    }
}

Came from:

• https://twitter.com/webdevilopers/status/969629343902248961