UuidItemTest.php

<?php

namespace Drupal\Tests\field\Kernel\String;

use Drupal\entity_test\Entity\EntityTest;
use Drupal\Tests\field\Kernel\FieldKernelTestBase;
use Drupal\Component\Uuid\Uuid;

/**
 * Tests the UUID field.
 *
 * @group field
 */
class UuidItemTest extends FieldKernelTestBase {
    
    /**
     * Tests 'uuid' random values.
     */
    public function testSampleValue() {
        $entity = EntityTest::create([]);
        $entity->save();
        $uuid_field = $entity->get('uuid');
        // Test the generateSampleValue() method.
        $uuid_field->generateSampleItems();
        $this->assertTrue(Uuid::isValid($uuid_field->value));
    }

}