RedirectOnExceptionTest.php

<?php

namespace Drupal\KernelTests\RequestProcessing;

use Drupal\KernelTests\KernelTestBase;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;

/**
 * Tests redirects on exception pages.
 *
 * @group request_processing
 */
class RedirectOnExceptionTest extends KernelTestBase {
    
    /**
     * {@inheritdoc}
     */
    protected static $modules = [
        'system',
        'test_page_test',
    ];
    public function testRedirectOn404() {
        \Drupal::configFactory()->getEditable('system.site')
            ->set('page.404', '/test-http-response-exception/' . Response::HTTP_PERMANENTLY_REDIRECT)
            ->save();
        
        /** @var \Symfony\Component\HttpKernel\HttpKernelInterface $http_kernel */
        $http_kernel = \Drupal::service('http_kernel');
        // Foo doesn't exist, so this triggers the 404 page.
        $request = Request::create('/foo');
        $response = $http_kernel->handle($request);
        $this->assertEquals(Response::HTTP_PERMANENTLY_REDIRECT, $response->getStatusCode());
    }

}