✨ 【第10章 テストに聞いてみる】 times の一般化のためにまずは currency を追加する

・Dollar, Francクラスを Money クラスと合わせるために currency のフィールドを追加する

src/__tests__/dollar.test.ts

@@ -4,6 +4,6 @@ import { Money, Dollar } from '../money';
 test('times', () => {
   const five: Money = Money.dollar(5);
 
-  expect(five.times(2)).toEqual(new Dollar(10));
-  expect(five.times(3)).toEqual(new Dollar(15));
+  expect(five.times(2)).toEqual(Money.dollar(10));
+  expect(five.times(3)).toEqual(Money.dollar(15));
 });

src/__tests__/franc.test.ts

@@ -4,7 +4,7 @@ import { Money, Franc } from '../money';
 test('times', () => {
   const five: Money = Money.franc(5);
 
-  expect(five.times(2)).toEqual(new Franc(10));
-  expect(five.times(3)).toEqual(new Franc(15));
+  expect(five.times(2)).toEqual(Money.franc(10));
+  expect(five.times(3)).toEqual(Money.franc(15));
 });
 

src/money.ts

@@ -6,11 +6,11 @@ export abstract class Money {
   }
 
   static dollar(amount: number):Dollar {
-    return new Dollar(amount)
+    return new Dollar(amount, 'USD')
   }
 
   static franc(amount: number):Franc {
-    return new Franc(amount)
+    return new Franc(amount, 'CHF')
   }
 
   abstract times(multiplier: number): Money
@@ -25,21 +25,21 @@ export abstract class Money {
 }
 
 export class Dollar extends Money {
-  constructor(amount: number) {
-    super(amount, 'USD');
+  constructor(amount: number, currency: string) {
+    super(amount, currency);
   }
 
   times(multiplier: number): Money {
-    return new Dollar(this.amount * multiplier)
+    return new Dollar(this.amount * multiplier, this.currency)
   }
 }
 
 export class Franc extends Money {
-  constructor(amount: number) {
-    super(amount, 'CHF');
+  constructor(amount: number, currency: string) {
+    super(amount, currency);
   }
 
   times(multiplier: number): Money {
-    return new Franc(this.amount * multiplier)
+    return new Franc(this.amount * multiplier, this.currency)
   }
 }