public function testSumPlusMoney() { $fiveBucks = Money::dollar(5); $tenFrancs = Money::franc(10); $bank = new Bank(); $bank->addRate('CHF', 'USD', 2); $step1 = new Sum($fiveBucks, $tenFrancs); $sum = $step1->plus($fiveBucks); $result = $bank->reduce($sum, 'USD'); $this->assertEquals(Money::dollar(15), $result); }