@Test
public void testLeq() {

    Stamp s1 = new Stamp();
    Stamp s2 = new Stamp();
    Assert.assertTrue(s1.leq(s2.event()));
    Assert.assertTrue(Causality.lessThanEquals(s1, s2.event()));
    Assert.assertFalse(s2.event().leq(s1));
    Assert.assertFalse(Causality.lessThanEquals(s2.event(), s1));
}