Adding Quickcheck for DGM graph (#1474)

Added quickcheck to test the structural properties of DGM graph, by checking its number of edges and nodes.

Co-authored-by: Ivan Carvalho <[email protected]>

Author: Krishn1412

rustworkx-core/tests/quickcheck/dorogovtsev_goltsev_mendes_graph.rs

@@ -0,0 +1,25 @@
+use petgraph::graph::Graph;
+use quickcheck::{quickcheck, TestResult};
+use rustworkx_core::generators::dorogovtsev_goltsev_mendes_graph;
+
+#[test]
+fn prop_dgm_graph_structure() {
+    fn prop(n: u8) -> TestResult {
+        let n = (n % 7) as usize;
+        let g: Graph<(), ()> = match dorogovtsev_goltsev_mendes_graph(n, || (), || ()) {
+            Ok(graph) => graph,
+            Err(_) => return TestResult::error("Failed to generate DGM graph"),
+        };
+
+        let expected_edges = 3_usize.pow(n as u32);
+        let expected_nodes = (expected_edges + 3) / 2;
+
+        if g.node_count() != expected_nodes || g.edge_count() != expected_edges {
+            return TestResult::failed();
+        }
+
+        TestResult::passed()
+    }
+
+    quickcheck(prop as fn(u8) -> TestResult);
+}

rustworkx-core/tests/quickcheck/main.rs

@@ -2,6 +2,7 @@ mod barbell_graph;
 mod binomial_tree_graph;
 mod complete_graph;
 mod cycle_graph;
+mod dorogovtsev_goltsev_mendes_graph;
 mod full_rary_tree_graph;
 mod grid_graph;
 mod heavy_hex_graph;