TestRouteSubscriber.php

<?php

namespace Drupal\devel_test\Routing;

use Drupal\Core\Routing\RouteSubscriberBase;
use Drupal\Core\State\State;
use Symfony\Component\Routing\RouteCollection;

/**
 * Router subscriber class for testing purpose.
 */
class TestRouteSubscriber extends RouteSubscriberBase {
    
    /**
     * The state store.
     *
     * @var Drupal\Core\State\State
     */
    protected $state;
    
    /**
     * Constructor method.
     *
     * @param Drupal\Core\State\State $state
     *   The object State.
     */
    public function __construct(State $state) {
        $this->state = $state;
    }
    
    /**
     * {@inheritdoc}
     */
    protected function alterRoutes(RouteCollection $collection) {
        $this->state
            ->set('devel_test_route_rebuild', 'Router rebuild fired');
    }

}