class FormElementMaxlengthTest

class FormElementMaxlengthTest extends KernelTestBase implements FormInterface {
    
    /**
     * {@inheritdoc}
     */
    protected static $modules = [
        'system',
    ];
    
    /**
     * {@inheritdoc}
     */
    public function getFormId() {
        return 'form_test_maxlength';
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildForm(array $form, FormStateInterface $form_state) {
        $form['title'] = [
            '#type' => 'textfield',
            '#maxlength' => 255,
        ];
        $form['description'] = [
            '#type' => 'textarea',
            '#maxlength' => 255,
        ];
        $form['submit'] = [
            '#type' => 'submit',
            '#value' => 'Submit',
        ];
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitForm(array &$form, FormStateInterface $form_state) {
    }
    
    /**
     * {@inheritdoc}
     */
    public function validateForm(array &$form, FormStateInterface $form_state) {
    }
    
    /**
     * Ensures maxlength attribute can be used in compatible elements.
     */
    public function testAttributes() : void {
        
        /** @var \Drupal\Core\Form\FormBuilderInterface $form_builder */
        $form_builder = $this->container
            ->get('form_builder');
        $form_state = new FormState();
        $elements = $form_builder->buildForm($this, $form_state);
        $this->render($elements);
        $css_selector_converter = new CssSelectorConverter();
        $elements = $this->xpath($css_selector_converter->toXPath('input[name=title][maxlength=255]'));
        $this->assertCount(1, $elements, 'Text field has correct maxlength in form.');
        $elements = $this->xpath($css_selector_converter->toXPath('textarea[name=description][maxlength=255]'));
        $this->assertCount(1, $elements, 'Textarea field has correct maxlength in form.');
    }

}