TestLoader.php

<?php

namespace Drupal\twig_loader_test\Loader;

use Twig\Loader\LoaderInterface;
use Twig\Source;

/**
 * A test Twig loader.
 */
class TestLoader implements LoaderInterface {
    
    /**
     * {@inheritdoc}
     */
    public function getSourceContext(string $name) : Source {
        $name = (string) $name;
        $value = $name === 'kittens' ? 'kittens' : 'cats';
        return new Source($value, $name);
    }
    
    /**
     * {@inheritdoc}
     */
    public function exists(string $name) {
        return TRUE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getCacheKey(string $name) : string {
        return $name;
    }
    
    /**
     * {@inheritdoc}
     */
    public function isFresh(string $name, int $time) : bool {
        return TRUE;
    }

}