    @Test
    public void testJoin() {

        Stamp expected = new Stamp(IDs.one(),
                Events.with(1, Events.zero(), Events.with(1)));

        assertEquals(expected, forkedStamp1.join(forkedStamp2));
        assertEquals(expected, forkedStamp2.join(forkedStamp1));
        assertNormalizedStamp(forkedStamp1.join(forkedStamp2));
    }