@Test
    public void edgeIsToggled()
    {
        Vertex v1 = vc.addVertex(3, 5);
        Vertex v2 = vc.addVertex(5, 3);
        vc.toggleEdge(v1, v2);
        boolean b1 = v1.getAdjacents().contains(v2) && v2.getAdjacents().contains(v1);
        vc.toggleEdge(v2, v1);
        boolean b2 = v1.getAdjacents().isEmpty() && v2.getAdjacents().isEmpty();
        assertTrue(b1 && b2);
    }