public void testPlus_Seconds() {
        Seconds test2 = Seconds.seconds(2);
        Seconds test3 = Seconds.seconds(3);
        Seconds result = test2.plus(test3);
        assertEquals(2, test2.getSeconds());
        assertEquals(3, test3.getSeconds());
        assertEquals(5, result.getSeconds());
        
        assertEquals(1, Seconds.ONE.plus(Seconds.ZERO).getSeconds());
        assertEquals(1, Seconds.ONE.plus((Seconds) null).getSeconds());
        
        try {
            Seconds.MAX_VALUE.plus(Seconds.ONE);
            fail();
        } catch (ArithmeticException ex) {
            // expected
        }
    }