✨ 【TODO】 丸め処理用の足し算メソッドを使用した書きぶりに変更

TODO.md

@@ -1,6 +1,6 @@
 - [ ] $5 + $5がMoneyを返す
-- [ ] Money の丸め処理どうする？
 
+- [x] Money の丸め処理どうする？
 - [x] 他のオブジェクトとの等価性比較
 - [x] 5CHF * 2 = 10CHF
 - [x] Sum.plus

src/__tests__/money.test.ts

@@ -50,7 +50,11 @@ test('test reduce sum', () => {
   const sum  = Money.dollar(3).plus(Money.dollar(4));
   const bank = new Bank();
   const reduced = bank.reduce(sum, 'USD');
-  expect(Money.dollar(7)).toEqual(reduced);
+  expect(reduced).toEqual(Money.dollar(7));
+
+  const sumDecimal = Money.dollar(0.7715).plus(Money.dollar(0.177));
+  const reducedDecimal = bank.reduce(sumDecimal, 'USD');
+  expect(reducedDecimal).toEqual(Money.dollar(0.9485));
 });
 
 test('test plus returns sum', () => {

src/sum.ts

@@ -1,10 +1,11 @@
 import { Bank } from "./bank";
-import { Expression } from "./expression";
+import { Expression, roundCalculate } from "./expression";
 import { Currency, Money } from "./money";
 
 export class Sum implements Expression {
   constructor(public augend: Expression, public addend: Expression) {
   }
+
   plus(addend: Expression): Expression {
     return new Sum(this, addend);
   }
@@ -14,9 +15,7 @@ export class Sum implements Expression {
   }
 
   reduce(bank: Bank, to: Currency):Money {
-    const amount :number =
-      this.augend.reduce(bank, to).amount
-      + this.addend.reduce(bank, to).amount
+    const amount :number = roundCalculate(this.augend.reduce(bank, to).amount, this.addend.reduce(bank, to).amount);
     return new Money(amount, to);
   }
 }