PreWarmerTest.php

<?php

declare (strict_types=1);
namespace Drupal\KernelTests\Core\PreWarm;

use Drupal\KernelTests\KernelTestBase;

/**
 * Tests the cache prewarmer.
 *
 * @group PreWarm
 */
class PreWarmerTest extends KernelTestBase {
    
    /**
     * Tests prewarming all caches.
     */
    public function testPreWarmAllCaches() : void {
        $prewarmer = \Drupal::service('cache_prewarmer');
        $this->assertTrue($prewarmer->preWarmAllCaches());
        $this->assertFalse($prewarmer->preWarmAllCaches());
    }
    
    /**
     * Tests prewarming one cache at a time.
     */
    public function testPreWarmOneCache() : void {
        $prewarmer = \Drupal::service('cache_prewarmer');
        // Make sure at least one prewarmable service actually gets called.
        $called = FALSE;
        while ($prewarmer->preWarmOneCache()) {
            $called = TRUE;
        }
        $this->assertTrue($called);
        $this->assertFalse($prewarmer->preWarmOneCache());
    }

}