ComponentRenderTest.php

<?php

declare (strict_types=1);
namespace Drupal\KernelTests\Component;

use Drupal\KernelTests\KernelTestBase;
use Symfony\Component\DomCrawler\Crawler;
use Symfony\Component\HttpFoundation\Request;

/**
 * Tests the correct rendering of components.
 *
 * @group sdc
 */
final class ComponentRenderTest extends KernelTestBase {
  
  /**
   * {@inheritdoc}
   */
  protected static $modules = [
    'system',
    'sdc_test',
  ];
  
  /**
   * Tests the CSS load order.
   */
  public function testCssOrder() : void {
    $this->container
      ->get('theme_installer')
      ->install([
      'sdc_theme_test',
    ]);
    $build = [
      '#type' => 'component',
      '#component' => 'sdc_theme_test:css-load-order',
      '#props' => [],
    ];
    \Drupal::state()->set('sdc_test_component', $build);
    $request = Request::create('/sdc-test-component');
    $response = $this->container
      ->get('http_kernel')
      ->handle($request);
    $output = $response->getContent();
    $crawler = new Crawler($output);
    // Assert that both CSS files are attached to the page.
    $this->assertNotEmpty($crawler->filter('link[rel="stylesheet"][href*="css-load-order.css"]'));
    $this->assertNotEmpty($crawler->filter('link[rel="stylesheet"][href*="css-order-dependent.css"]'));
    $all_stylesheets = $crawler->filter('link[rel="stylesheet"]');
    $component_position = NULL;
    $dependent_position = NULL;
    foreach ($all_stylesheets as $index => $stylesheet) {
      $href = $stylesheet->attributes
        ->getNamedItem('href')->nodeValue;
      if (str_contains($href, 'css-load-order.css')) {
        $component_position = $index;
      }
      if (str_contains($href, 'css-order-dependent.css')) {
        $dependent_position = $index;
      }
    }
    // This will assert that css-order-dependent.css is loaded before the
    // component's css-load-order.css.
    $this->assertGreaterThan($dependent_position, $component_position);
  }

}