FormTestDisabledElementsForm example

  }

  /** * Tests handling of disabled elements. * * @see _form_test_disabled_elements() */
  public function testDisabledElements() {
    // Get the raw form in its original state.     $form_state = new FormState();
    $form = (new FormTestDisabledElementsForm())->buildForm([], $form_state);

    // Build a submission that tries to hijack the form by submitting input for     // elements that are disabled.     $edit = [];
    foreach (Element::children($form) as $key) {
      if (isset($form[$key]['#test_hijack_value'])) {
        if (is_array($form[$key]['#test_hijack_value'])) {
          foreach ($form[$key]['#test_hijack_value'] as $subkey => $value) {
            $edit[$key . '[' . $subkey . ']'] = $value;
          }
        }