public function testAdd()
{
$bn = new BigNumber(2147483647);
$this->assertSame($bn, $bn->add('9223372036854775808'));
$this->assertSame('9223372039002259455', $bn->getValue());
$bn->setScale(3);
$this->assertSame('9223372039002259457.250', $bn->add(2.25)->getValue());
}