preview();
$output = \Drupal::service('renderer')->renderRoot($output);
// Check that an empty class attribute is not added if the wrapper class is
// not set.
$this->assertTrue(strpos($output, '
') !== FALSE, 'Empty class is not added to DIV when class is not set');
// Check that an empty class attribute is not added if the list class is
// not set.
$this->assertTrue(strpos($output, '
') !== FALSE, 'Empty class is not added to UL when class is not set');
// Set wrapper class and list class in style options.
$view->style_plugin->options['class'] = 'class';
$view->style_plugin->options['wrapper_class'] = 'wrapper-class';
$output = $view->preview();
$output = \Drupal::service('renderer')->renderRoot($output);
// Check that class attribute is present if the wrapper class is set.
$this->assertTrue(strpos($output, '
') !== FALSE, 'Class is added to DIV');
// Check that class attribute is present if the list class is set.
$this->assertTrue(strpos($output, '