TestControllers.php

<?php

namespace Drupal\paramconverter_test;

use Drupal\Core\Entity\EntityInterface;
use Drupal\node\NodeInterface;

/**
 * Controller routine for testing the paramconverter.
 */
class TestControllers {
    public function testUserNodeFoo(EntityInterface $user, NodeInterface $node, $foo) {
        $foo = is_object($foo) ? $foo->label() : $foo;
        return [
            '#markup' => "user: {$user->label()}, node: {$node->label()}, foo: {$foo}",
        ];
    }
    public function testNodeSetParent(NodeInterface $node, NodeInterface $parent) {
        return [
            '#markup' => "Setting '{$parent->label()}' as parent of '{$node->label()}'.",
        ];
    }
    public function testEntityLanguage(NodeInterface $node) {
        $build = [
            '#markup' => $node->label(),
        ];
        \Drupal::service('renderer')->addCacheableDependency($build, $node);
        return $build;
    }

}