$request = new InternalRequest();
        $request = $request->withPageId(1);
        $request = $request->withLanguageId($languageUid);
        $requestContext = new InternalRequestContext();
        $requestContext = $requestContext->withBackendUserId(1);
        $html = (string) $this->executeFrontendSubRequest($request, $requestContext)->getBody();

<?php

declare(strict_types=1);

return [
    'pages' => [
        [
            'uid' => 1,
            'pid' => 0,
            'title' => 'Page with uid 1 below 0',
            'deleted' => 0,
            'backend_layout' => 'pagets__21',
            'slug' => '/start',
        ],
    ],
    'be_users' => [
        [
            'uid' => 1,
            'pid' => 0,
            'tstamp' => 1366642540,
            'username' => 'editor',
            // The actual password is: password
            'password' => '$1$tCrlLajZ$C0sikFQQ3SWaFAZ1Me0Z/1',
            'admin' => 0,
            'disable' => 0,
            'starttime' => 0,
            'endtime' => 0,
            'options' => 0,
            'crdate' => 1366642540,
            'workspace_perms' => 1,
            'deleted' => 0,
            'TSconfig' => null,
            'lastlogin' => 1371033743,
            'workspace_id' => 0,
            // Necessary to allow user to access this page.
            'db_mountpoints' => 1,
            // Necessary to open admin panel.
            'uc' => serialize([
                'AdminPanel' => [
                    'display_top' => true,
                ],
            ]),
        ],
    ],
];