SettingsConfigValidationTest.php

<?php

declare (strict_types=1);
namespace Drupal\Tests\image\Kernel;

use Drupal\Core\Config\Schema\SchemaIncompleteException;
use Drupal\KernelTests\KernelTestBase;

/**
 * @group image
 */
class SettingsConfigValidationTest extends KernelTestBase {
    
    /**
     * {@inheritdoc}
     */
    protected static $modules = [
        'image',
        'system',
    ];
    
    /**
     * Tests that the preview_image setting must be an existing image file.
     */
    public function testPreviewImagePathIsValidated() : void {
        $this->installConfig('image');
        // Drupal does not have a hard dependency on the fileinfo extension and
        // implements an extension-based mimetype guesser. Therefore, we must use
        // an incorrect extension here instead of writing text to a supposed PNG
        // file and depending on a check of the file contents.
        $file = sys_get_temp_dir() . '/fake_image.png.txt';
        file_put_contents($file, 'Not an image!');
        $this->expectException(SchemaIncompleteException::class);
        $this->expectExceptionMessage('[preview_image] This file is not a valid image.');
        $this->config('image.settings')
            ->set('preview_image', $file)
            ->save();
    }

}