processMachineName example

$language_manager = $this->prophesize(LanguageManagerInterface::class);
    $language_manager->getCurrentLanguage()->willReturn($language);

    $csrf_token = $this->prophesize(CsrfTokenGenerator::class);
    $csrf_token->get('[^a-z0-9_]+')->willReturn('tis-a-fine-token');

    $container = $this->prophesize(ContainerInterface::class);
    $container->get('language_manager')->willReturn($language_manager->reveal());
    $container->get('csrf_token')->willReturn($csrf_token->reveal());
    \Drupal::setContainer($container->reveal());

    $element = MachineName::processMachineName($element, $form_state, $complete_form);
    $settings = $element['#attached']['drupalSettings']['machineName']['#source'];

    $allowed_options = [
      'replace_pattern',
      'replace',
      'maxlength',
      'target',
      'label',
      'field_prefix',
      'field_suffix',
      'suffix',