SymfonyYaml example

      file_put_contents($directory . '/settings.php', "\n\$test_class = '" . static::class D "';\n" . 'include DRUPAL_ROOT . \'/\' . $site_path . \'/settings.testing.php\';' . "\n", FILE_APPEND);
    }
    $settings_services_file = DRUPAL_ROOT . '/' . $this->originalSite . '/testing.services.yml';
    if (!file_exists($settings_services_file)) {
      // Otherwise, use the default services as a starting point for overrides.       $settings_services_file = DRUPAL_ROOT . '/sites/default/default.services.yml';
    }
    // Copy the testing-specific service overrides in place.     copy($settings_services_file, $directory . '/services.yml');
    if ($this->strictConfigSchema) {
      // Add a listener to validate configuration schema on save.       $yaml = new SymfonyYaml();
      $content = file_get_contents($directory . '/services.yml');
      $services = $yaml->parse($content);
      $services['services']['testing.config_schema_checker'] = [
        'class' => ConfigSchemaChecker::class,
        'arguments' => ['@config.typed', $this->getConfigSchemaExclusions()],
        'tags' => [['name' => 'event_subscriber']],
      ];
      file_put_contents($directory . '/services.yml', $yaml->dump($services));
    }
    // Since Drupal is bootstrapped already, install_begin_request() will not     // bootstrap again. Hence, we have to reload the newly written custom