### Question:
Money implements IMoney { public boolean isZero() { return amount() == 0; } Money(int amount, String currency); IMoney add(IMoney m); IMoney addMoney(Money m); IMoney addMoneyBag(MoneyBag s); int amount(); String currency(); @Override boolean equals(Object anObject); @Override int hashCode(); boolean isZero(); IMoney multiply(int factor); IMoney negate(); IMoney subtract(IMoney m); @Override String toString(); void appendTo(MoneyBag m);  }### Answer:
@Test public void testIsZero() { assertTrue(fMB1.subtract(fMB1).isZero()); assertTrue(MoneyBag.create(new Money(0, "CHF"), new Money(0, "USD")).isZero()); }