getFormWithLimitedProperties example

    // the description is placed after the form element.     $field_id = 'edit-form-textfield-test-description-invisible';
    $description_id = $field_id . '--description';
    // Verify that the #description element is visually-hidden.     $this->assertSession()->elementExists('xpath', '//input[@id="' . $field_id . '" and @aria-describedby="' . $description_id . '"]/following-sibling::div[contains(@class, "visually-hidden")]');
  }

  /** * Tests forms in theme-less environments. */
  public function testFormsInThemeLessEnvironments() {
    $form = $this->getFormWithLimitedProperties();
    $render_service = $this->container->get('renderer');
    // This should not throw any notices.     $render_service->renderPlain($form);
  }

  /** * Return a form with element with not all properties defined. */
  protected function getFormWithLimitedProperties() {
    $form = [];