@Override
    public NetworkId networkId() {
        return networkId;
    }
@Test
    public void testEquality() {
        DefaultVirtualDevice device1 =
                new DefaultVirtualDevice(NetworkId.networkId(0), DID1);
        DefaultVirtualDevice device2 =
                new DefaultVirtualDevice(NetworkId.networkId(0), DID1);
        DefaultVirtualDevice device3 =
                new DefaultVirtualDevice(NetworkId.networkId(0), DID2);
        DefaultVirtualDevice device4 =
                new DefaultVirtualDevice(NetworkId.networkId(1), DID1);

        new EqualsTester().addEqualityGroup(device1, device2).addEqualityGroup(device3)
                .addEqualityGroup(device4).testEquals();
    }