public function testSumTimes()
{
$fiveBucks = Money::dollar(5);
$tenFrancs = Money::franc(10);
$bank = new Bank();
$bank->addRate('CHF', 'USD', 2);
$step1 = new Sum($fiveBucks, $tenFrancs);
$sum = $step1->times(2);
$result = $bank->reduce($sum, 'USD');
$this->assertEquals(Money::dollar(20), $result);
}