/**
 * Implements hook_search_preprocess().
 */
function {{ machine_name }}_search_preprocess($text, $langcode = NULL) {
  // If the language is not set, get it from the language manager.
  if (!isset($langcode)) {
    $langcode = \Drupal::languageManager()->getCurrentLanguage()->getId();
  }

  // If the langcode is set to 'en' then add variations of the word "testing"
  // which can also be found during English language searches.
  if ($langcode == 'en') {
    // Add the alternate verb forms for the word "testing".
    if ($text == 'we are testing') {
      $text .= ' test tested';
    }
  }

  return $text;
}