PHPSpec\Matcher\StartIteratingAsMatcher::supports PHP Метод

    public function supports($name, $subject, array $arguments)
    {
        return in_array($name, ['startIteratingAs', 'startYielding']) && 1 === count($arguments) && ($subject instanceof \Traversable || is_array($subject)) && ($arguments[0] instanceof \Traversable || is_array($arguments[0]));
    }