「Let's Play TDD #1: How Does This Thing Work, Again?」の写経 http://www.takaiwa.net/2014/01/lets-play-tdd-1-how-does-this-thing.html

_SavingsAccountTest.java

package com.jamesshore.screencast;

import static org.junit.Assert.*;
import org.junit.*;
/**
 * <p>
 * Let's Play TDD #1: How Does This Thing Work, Again?
 * https://www.youtube.com/watch?v=f3G7gu1IHws
 * </p>
 * Current Source code:
 * https://www.youtube.com/watch?v=f3G7gu1IHws&t=495
 *
 * @author takaiwa.net
 */
public class _SavingsAccountTest {

    @Test
    public void depositAndWithdrawal() {
        SavingAccount account = new SavingAccount();
        account.deposit(100);
        assertEquals("after deposit", 100, account.balance());
        account.withdraw(50);
        assertEquals("after withdrawal", 50,  account.balance());
    }

    @Test
    public void negativeBalanceIsJustFine() {
        SavingAccount account = new SavingAccount();
        account.withdraw(75);
        assertEquals(-75,  account.balance());
    }
}

SavingAccount.java

package com.jamesshore.screencast;
/**
 * <p>
 * Let's Play TDD #1: How Does This Thing Work, Again?
 * https://www.youtube.com/watch?v=f3G7gu1IHws
 * </p>
 * Current Source code:
 * https://www.youtube.com/watch?v=f3G7gu1IHws&t=504
 *
 * @author takaiwa.net
 */
public class SavingAccount {

    private int balance = 0;

    public void deposit(int amount) {
        balance += amount;
    }

    public int balance() {
        return balance;
    }

    public void withdraw(int amount) {
        balance -= amount;
    }
}