/** . */
  public void testIsGraphConnected() {
    Pseudograph<String, DefaultEdge> g = create();
    ConnectivityInspector<String, DefaultEdge> inspector =
        new ConnectivityInspector<String, DefaultEdge>(g);

    assertEquals(false, inspector.isGraphConnected());

    g.removeVertex(V4);
    inspector = new ConnectivityInspector<String, DefaultEdge>(g);
    assertEquals(true, inspector.isGraphConnected());

    g.removeVertex(V1);
    assertEquals(1, g.edgeSet().size());

    g.removeEdge(e2);
    g.addEdge(V2, V2);
    assertEquals(1, g.edgeSet().size());

    inspector = new ConnectivityInspector<String, DefaultEdge>(g);
    assertEquals(false, inspector.isGraphConnected());
  }
  /**
   * .
   *
   * @return a graph
   */
  public Pseudograph<String, DefaultEdge> create() {
    Pseudograph<String, DefaultEdge> g = new Pseudograph<String, DefaultEdge>(DefaultEdge.class);

    assertEquals(0, g.vertexSet().size());
    g.addVertex(V1);
    assertEquals(1, g.vertexSet().size());
    g.addVertex(V2);
    assertEquals(2, g.vertexSet().size());
    g.addVertex(V3);
    assertEquals(3, g.vertexSet().size());
    g.addVertex(V4);
    assertEquals(4, g.vertexSet().size());

    assertEquals(0, g.edgeSet().size());

    e1 = g.addEdge(V1, V2);
    assertEquals(1, g.edgeSet().size());

    e2 = g.addEdge(V2, V3);
    assertEquals(2, g.edgeSet().size());

    e3 = g.addEdge(V3, V1);
    assertEquals(3, g.edgeSet().size());

    e3_b = g.addEdge(V3, V1);
    assertEquals(4, g.edgeSet().size());
    assertNotNull(e3_b);

    u = g.addEdge(V1, V1);
    assertEquals(5, g.edgeSet().size());
    u = g.addEdge(V1, V1);
    assertEquals(6, g.edgeSet().size());

    return g;
  }