@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));
}