@Override
    public Set<Path> getPaths(ElementId src, ElementId dst) {
        checkPermission(TOPOLOGY_READ);

        return getPaths(src, dst, (LinkWeigher) null);
    }
@Test
    public void noEdge() {
        Set<Path> paths = service.getPaths(hid("12:34:56:78:90:ab/1"),
                                           hid("12:34:56:78:90:ef/1"));
        assertTrue("there should be no paths", paths.isEmpty());
    }