Node node1 = factory.newNode();
Node node2 = factory.newNode();
Node node3 = factory.newNode();
graph.addNode(node1);
graph.addNode(node2);
graph.addNode(node3);
//Test normal edge
graph.addEdge(node1, node2);
AbstractNode preNode1 = (AbstractNode) node1;
AbstractNode preNode2 = (AbstractNode) node2;