Yosymfony\Spress\Core\Support\StringWrapper::lower PHP Method

    public function lower()
    {
        return mb_strtolower($this->str, 'UTF-8');
    }

 public function testLowerCyrillic()
 {
     $str = new StringWrapper('баШ');
     $this->assertEquals('баш', $str->lower());
 }