public void TestCreateNestedStructures()
{
// Documentation:
// Subgraphs are an important construct in Cgraph.They are intended for organizing subsets of
// graph objects and can be used interchangeably with top - level graphs in almost all Cgraph
// functions. A subgraph may contain any nodes or edges of its parent. (When an edge is
// inserted in a subgraph, its nodes are also implicitly inserted if necessary.Similarly,
// insertion of a node or edge automatically implies insertion in all containing subgraphs up
// to the root.) Subgraphs of a graph form a hierarchy(a tree).Cgraph has functions to
// create, search, and iterate over subgraphs.
// Conclusion: the hierarchical tree structure is maintained in a sane way across all
// operations we can do w.r.t. subgraphs.
// If a node is created in a subgraph, it should also be contained in all supergraphs
RootGraph graph = Utils.CreateUniqueTestGraph();
SubGraph supergraph = graph.GetOrAddSubgraph("level 1");
string subgraphname = "level 2";
SubGraph subgraph = supergraph.GetOrAddSubgraph(subgraphname);
string nodename = "test node";
Node node = subgraph.GetOrAddNode(nodename);
// Node must be contained in super graph
Assert.True(node.MyRootGraph.Equals(graph));
Assert.True(supergraph.Contains(node));
Assert.True(supergraph.Nodes().Contains(node));
Assert.NotNull(supergraph.GetNode(nodename));
// Node must be contained in root graph
Assert.True(graph.Contains(node));
Assert.True(graph.Nodes().Contains(node));
Assert.NotNull(graph.GetNode(nodename));
// Subgraph must be contained in super graph
Assert.True(supergraph.Contains(subgraph));
Assert.True(supergraph.Descendants().Contains(subgraph));
Assert.NotNull(supergraph.GetSubgraph(subgraphname));
// Subgraph must be contained in root graph
Assert.True(graph.Contains(subgraph));
Assert.True(graph.Descendants().Contains(subgraph));
// Subgraph cannot be obtained in the following way:
//graph.GetSubgraph(subgraphname)
Assert.Null(graph.GetSubgraph(subgraphname));
// Use a utility function instead:
Assert.NotNull(graph.GetDescendantByName(subgraphname));
}