public void Test_ClearGraph()
        {
            GraphVizProcessor gvp = new GraphVizProcessor();

            gvp.graph = new Graph(GraphType.Digraph, new Stmt_list());

            gvp.AddNode("a");

            gvp.ClearGraph();

            if (gvp.NodeExists("a"))
            {
                Assert.Fail("Node found after clearing graph.");
            }
        }