public void testMinus_Weeks() {
        Weeks test2 = Weeks.weeks(2);
        Weeks test3 = Weeks.weeks(3);
        Weeks result = test2.minus(test3);
        assertEquals(2, test2.getWeeks());
        assertEquals(3, test3.getWeeks());
        assertEquals(-1, result.getWeeks());
        
        assertEquals(1, Weeks.ONE.minus(Weeks.ZERO).getWeeks());
        assertEquals(1, Weeks.ONE.minus((Weeks) null).getWeeks());
        
        try {
            Weeks.MIN_VALUE.minus(Weeks.ONE);
            fail();
        } catch (ArithmeticException ex) {
            // expected
        }
    }