Codeception\Module\WPLoader::_switch_theme PHP Method

    public function _switch_theme()
    {
        if (!empty($this->config['theme'])) {
            $stylesheet = is_array($this->config['theme']) ? end($this->config['theme']) : $this->config['theme'];
            $functionsFile = $this->wp->WP_CONTENT_DIR() . '/themes/' . $stylesheet . '/functions.php';
            if (file_exists($functionsFile)) {
                require_once $functionsFile;
            }
            call_user_func([$this->wp, 'switch_theme'], $stylesheet);
            $this->wp->do_action('after_switch_theme', $stylesheet);
        }
    }