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@TomckySan TomckySan/main.js
Created Jan 5, 2018

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「テスト駆動開発」JS(AVA)
class Bank {
constructor() {
this.rates = new Map();
}
reduce(source, to) {
return source.reduce(this, to);
}
addRate(from, to, rate) {
this.rates.set(`${from}_${to}`, rate);
}
rate(from, to) {
if (from === to) return 1;
return this.rates.get(`${from}_${to}`);
}
}
class Sum {
constructor(augend, addend) {
this.augend = augend;
this.addend = addend;
}
times(multiplier) {
return new Sum(this.augend.times(multiplier), this.addend.times(multiplier));
}
plus(addend) {
return new Sum(this, addend);
}
reduce(bank, to) {
const amount = this.augend.reduce(bank, to).amount + this.addend.reduce(bank, to).amount;
return new Money(amount, to);
}
}
class Money {
constructor(amount, currency) {
this.amount = amount;
this.currency = currency;
}
times(multiplier) {
return new Money(this.amount * multiplier, this.currency);
}
plus(addend) {
return new Sum(this, addend);
}
reduce(bank, to) {
const rate = bank.rate(this.currency, to);
return new Money(this.amount / rate, to);
}
getCurrency() {
return this.currency;
}
equals(money) {
return this.amount === money.amount && this.currency === money.getCurrency();
}
static dollar(amount) {
return new Money(amount, 'USD');
}
static franc(amount) {
return new Money(amount, 'CHF');
}
}
export { Bank, Sum, Money }
import test from 'ava';
import 'babel-register';
import { Bank, Sum, Money } from '../src/js/main';
test('Test Multiplication.', t => {
const five = Money.dollar(5);
t.is(Money.dollar(10).amount, five.times(2).amount);
t.is(Money.dollar(15).amount, five.times(3).amount);
});
test('Test Equality.', t => {
t.true(Money.dollar(5).equals(Money.dollar(5)));
t.false(Money.dollar(5).equals(Money.dollar(6)));
// ドルとフランが一緒じゃないことをテストする
t.false(Money.dollar(5).equals(Money.franc(5)));
});
test('Test Currency.', t => {
t.is('USD', Money.dollar(1).getCurrency());
t.is('CHF', Money.franc(1).getCurrency());
});
test('Test Simple Addition.', t => {
const five = Money.dollar(5);
const sum = five.plus(five);
const bank = new Bank();
const reduced = bank.reduce(sum, 'USD');
t.true(Money.dollar(10).equals(reduced));
});
test('Test Plus Returns Sum.', t => {
const five = Money.dollar(5);
const sum = five.plus(five);
t.true(five.equals(sum.augend));
t.true(five.equals(sum.addend));
});
test('Test Reduce Sum.', t => {
const sum = new Sum(Money.dollar(3), Money.dollar(4));
const bank = new Bank();
const result = bank.reduce(sum, 'USD');
t.true(Money.dollar(7).equals(result));
});
test('Test Reduce Money.', t => {
const bank = new Bank();
const result = bank.reduce(Money.dollar(1), 'USD');
t.true(Money.dollar(1).equals(result));
});
test('Test Reduce Money Different Currency.', t => {
const bank = new Bank();
bank.addRate('CHF', 'USD', 2);
const result = bank.reduce(Money.franc(2), 'USD');
t.true(Money.dollar(1).equals(result));
});
test('Test Identity Rate.', t => {
t.is(1, new Bank().rate('USD', 'USD'));
});
test('Test Identity Rate.', t => {
const bank = new Bank();
bank.addRate('CHF', 'USD', 2);
t.is(2, bank.rate('CHF', 'USD'));
});
test('Test Mixed Addision.', t => {
const fiveBucks = Money.dollar(5);
const tenFrancs = Money.franc(10);
const bank = new Bank();
bank.addRate('CHF', 'USD', 2);
const result = bank.reduce(fiveBucks.plus(tenFrancs), 'USD');
t.true(Money.dollar(10).equals(result));
});
test('Test Sum Plus Money.', t => {
const fiveBucks = Money.dollar(5);
const tenFrancs = Money.franc(10);
const bank = new Bank();
bank.addRate('CHF', 'USD', 2);
const sum = new Sum(fiveBucks, tenFrancs).plus(fiveBucks);
const result = bank.reduce(sum, 'USD');
t.true(Money.dollar(15).equals(result));
});
test('Test Sum Times.', t => {
const fiveBucks = Money.dollar(5);
const tenFrancs = Money.franc(10);
const bank = new Bank();
bank.addRate('CHF', 'USD', 2);
const sum = new Sum(fiveBucks, tenFrancs).times(2);
const result = bank.reduce(sum, 'USD');
t.true(Money.dollar(20).equals(result));
});
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