@Test
    public void removingSingleVertexThatIsANeighbour() {
        l.addVertex(v);
        l.addVertex(k);
        l.addEdge(v, k);
        l.removeVertex(1);
        assertTrue(l.getNeighbours(0).contains(v)
                && !l.getNeighbours(0).contains(k));
    }