public function testUcfirst()
{
$this->eq(s::ucfirst('abc'), 'Abc');
$this->eq(s::ucfirst(''), '');
$this->eq(s::upperFirst('abc'), 'Abc');
$this->eq(s::capitalize('abc'), 'Abc');
}
public function upperFirst()
{
return new self(s::upperFirst($this->value));
}