trait ConfigTestTrait in Drupal 8

trait ConfigTestTrait {
  use StorageCopyTrait;

  /**
   * Returns a ConfigImporter object to import test configuration.
   *
   * @return \Drupal\Core\Config\ConfigImporter
   *   The config importer object.
   */
  protected function configImporter() {
    if (!$this->configImporter) {

      // Set up the ConfigImporter object for testing.
      $storage_comparer = new StorageComparer($this->container
        ->get('config.storage.sync'), $this->container
        ->get('config.storage'));
      $this->configImporter = new ConfigImporter($storage_comparer, $this->container
        ->get('event_dispatcher'), $this->container
        ->get('config.manager'), $this->container
        ->get('lock'), $this->container
        ->get('config.typed'), $this->container
        ->get('module_handler'), $this->container
        ->get('module_installer'), $this->container
        ->get('theme_handler'), $this->container
        ->get('string_translation'), $this->container
        ->get('extension.list.module'));
    }

    // Always recalculate the changelist when called.
    return $this->configImporter
      ->reset();
  }

  /**
   * Copies configuration objects from source storage to target storage.
   *
   * @param \Drupal\Core\Config\StorageInterface $source_storage
   *   The source config storage service.
   * @param \Drupal\Core\Config\StorageInterface $target_storage
   *   The target config storage service.
   */
  protected function copyConfig(StorageInterface $source_storage, StorageInterface $target_storage) {
    static::replaceStorageContents($source_storage, $target_storage);
  }

}