@Test(expected = RuntimeException.class)
    public void twoInchesPlusEightOuncesShouldThrowException(){

        ArithmeticQuantity two_in = new ArithmeticQuantity(2, Distance.INCHES);
        ArithmeticQuantity eight_oz = new ArithmeticQuantity(8, Volume.OUNCE);
        two_in.add(eight_oz);
    }