TestFieldConstraint.php

<?php

namespace Drupal\field_test\Plugin\Validation\Constraint;

use Drupal\Core\StringTranslation\TranslatableMarkup;
use Drupal\Core\Validation\Attribute\Constraint;
use Symfony\Component\Validator\Constraints\NotEqualTo;

/**
 * Checks if a value is not equal.
 */
class TestFieldConstraint extends NotEqualTo {
  
  /**
   * {@inheritdoc}
   */
  public function getRequiredOptions() {
    return [
      'value',
    ];
  }
  
  /**
   * {@inheritdoc}
   */
  public function validatedBy() {
    return '\\Symfony\\Component\\Validator\\Constraints\\NotEqualToValidator';
  }

}