@Override
    public Set<Host> getConnectedHosts(ConnectPoint connectPoint) {
        checkNotNull(connectPoint, "Connect point cannot be null");
        return filter(getHostsColl(), host -> host.location().equals(connectPoint));
    }
@Test(expected = NullPointerException.class)
    public void testGetConnectedHostsByNullLoc() {
        VirtualNetwork vnet = setupEmptyVnet();
        HostService hostService = manager.get(vnet.id(), HostService.class);

        hostService.getConnectedHosts((ConnectPoint) null);
    }