Hal\MutaTesting\Event\Subscriber\Format\ConsoleSubscriber::onMutation PHP Method

    public function onMutation(MutationEvent $event)
    {
        if (!$event->getUnit()) {
            $this->progress('<error>E</error>');
            return;
        }
        if (!$event->getUnit()->hasFail()) {
            $this->progress('L');
        } else {
            $this->progress('.');
        }
    }