TestRouteAttributeForm.php

<?php

declare (strict_types=1);
namespace Drupal\router_test\Form;

use Drupal\Core\Form\FormBase;
use Drupal\Core\Form\FormStateInterface;
use Symfony\Component\Routing\Attribute\Route;

/**
 * Test form object for Route attribute.
 */
class TestRouteAttributeForm extends FormBase {
  
  /**
   * {@inheritdoc}
   */
  public function getFormId() : string {
    return 'router_test';
  }
  
  /**
   * {@inheritdoc}
   */
  public function buildForm(array $form, FormStateInterface $form_state) : array {
    $form['button'] = [
      '#type' => 'submit',
      '#value' => 'Click here',
    ];
    return $form;
  }
  
  /**
   * {@inheritdoc}
   */
  public function submitForm(array &$form, FormStateInterface $form_state) : void {
  }

}