private PiMulticastGroupEntry(int groupId, Set<PiPreReplica> replicas) {
        this.groupId = groupId;
        this.replicas = replicas;
    }
@Test
    public void testPiMulticastGroupEntry() {
        assertThat("Invalid group ID",
                   group1.groupId(), is(groupId1));
        assertThat("Invalid replicas size",
                   group1.replicas().size(), is(2));
        assertThat("Invalid replicas",
                   group1.replicas(), contains(replica1, replica2));

        assertThat("Invalid group ID",
                   group2.groupId(), is(groupId2));
        assertThat("Invalid replicas size",
                   group2.replicas().size(), is(3));
        assertThat("Invalid replicas",
                   group2.replicas(), contains(replica1, replica2, replica3));
    }