EntityTestUniqueConstraint.php

<?php

declare (strict_types=1);
namespace Drupal\entity_test\Entity;

use Drupal\content_translation\ContentTranslationHandler;
use Drupal\Core\Entity\Attribute\ContentEntityType;
use Drupal\Core\StringTranslation\TranslatableMarkup;
use Drupal\Core\Entity\EntityTypeInterface;
use Drupal\Core\Field\BaseFieldDefinition;
use Drupal\entity_test\EntityTestAccessControlHandler;
use Drupal\entity_test\EntityTestForm;
use Drupal\entity_test\EntityTestViewBuilder as TestViewBuilder;

/**
 * Defines a test entity class for unique constraint.
 */
class EntityTestUniqueConstraint extends EntityTest {
    
    /**
     * {@inheritdoc}
     */
    public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
        $fields = parent::baseFieldDefinitions($entity_type);
        $fields['field_test_text'] = BaseFieldDefinition::create('string')->setLabel(t('unique_field_test'))
            ->setCardinality(3)
            ->addConstraint('UniqueField');
        $fields['field_test_reference'] = BaseFieldDefinition::create('entity_reference')->setLabel(t('unique_reference_test'))
            ->setCardinality(2)
            ->addConstraint('UniqueField')
            ->setSetting('target_type', 'user');
        return $fields;
    }

}