Segment::group PHP Method

    public static function group(array $message)
    {
        self::checkClient();
        $groupId = !empty($message["groupId"]);
        $userId = !empty($message["userId"]);
        self::assert($groupId && $userId, "Segment::group() expects userId and groupId");
        return self::$client->group($message);
    }

 function testEmptyArrayTraits()
 {
     $this->assertTrue(Segment::identify(array("userId" => "empty-traits", "traits" => array())));
     $this->assertTrue(Segment::group(array("userId" => "empty-traits", "groupId" => "empty-traits", "traits" => array())));
 }