public WithSingleDependencyChain()
 {
     _graph = new DependencyGraph <string>();
     _graph.AddNode("3");
     _graph.AddNode("0");
     _graph.AddNode("1");
     _graph.AddNode("2");
     _graph.Connect("3", "1");
     _graph.Connect("3", "2");
     _graph.Connect("2", "1");
     _graph.Connect("1", "0");
 }