Adding Quickcheck for heavy hex graph (#1469)

To ensure the structural properties of heavy hex graph hold, we check that for every odd d < 31,
The total number of nodes equals the theoretical count:
(
5
d
2
−
2
d
−
1
)
/
2
(5d
2
 −2d−1)/2
The total number of edges equals:
2
d
(
d
−
1
)
+
(
d
+
1
)
(
d
−
1
)
2d(d−1)+(d+1)(d−1)

Author: Krishn1412

rustworkx-core/tests/quickcheck/heavy_hex_graph.rs

@@ -0,0 +1,28 @@
+use petgraph::graph::UnGraph;
+use quickcheck::{quickcheck, TestResult};
+use rustworkx_core::generators::heavy_hex_graph;
+
+#[test]
+fn prop_heavy_hex_structure() {
+    fn prop(d: usize) -> TestResult {
+        let d = (d % 31) | 1;
+        if d == 0 {
+            return TestResult::discard();
+        }
+
+        let g = match heavy_hex_graph::<UnGraph<(), ()>, (), _, _, ()>(d, || (), || (), false) {
+            Ok(g) => g,
+            Err(_) => return TestResult::error("Unexpected error in graph generation"),
+        };
+
+        let expected_nodes = (5 * d * d - 2 * d - 1) / 2;
+        let expected_edges = 2 * d * (d - 1) + (d + 1) * (d - 1);
+
+        let node_ok = g.node_count() == expected_nodes;
+        let edge_ok = g.edge_count() == expected_edges;
+
+        TestResult::from_bool(node_ok && edge_ok)
+    }
+
+    quickcheck(prop as fn(usize) -> TestResult);
+}

rustworkx-core/tests/quickcheck/main.rs

@@ -1,4 +1,5 @@
 mod barbell_graph;
 mod full_rary_tree_graph;
 mod grid_graph;
+mod heavy_hex_graph;
 mod lollipop_graph;