Adding quickcheck for Heavy Square graph (#1475)

Checking the structural properties by verifying the node and edge count. Ensuring no graph is generated for even d, and if bidirectionality holds.

Author: Krishn1412

rustworkx-core/tests/quickcheck/heavy_square_graph.rs

@@ -0,0 +1,78 @@
+use petgraph::graph::Graph;
+use petgraph::visit::EdgeRef;
+use quickcheck::{quickcheck, TestResult};
+use rustworkx_core::generators::heavy_square_graph;
+use std::collections::HashSet;
+
+#[test]
+fn prop_heavy_square_graph_structure() {
+    fn prop(d: u8) -> TestResult {
+        let d = ((d % 11) | 1) as usize; // ensure d is odd
+        if d == 0 {
+            return TestResult::discard();
+        }
+
+        let g: Graph<(), ()> = match heavy_square_graph(d, || (), || (), false) {
+            Ok(graph) => graph,
+            Err(_) => return TestResult::error("Failed to generate heavy square graph"),
+        };
+
+        let expected_nodes = 3 * d * d - 2 * d;
+        let expected_edges = 4 * d * (d - 1);
+
+        if g.node_count() != expected_nodes || g.edge_count() != expected_edges {
+            return TestResult::failed();
+        }
+
+        TestResult::passed()
+    }
+
+    quickcheck(prop as fn(u8) -> TestResult);
+}
+
+#[test]
+fn prop_heavy_square_bidirectionality() {
+    fn prop(d: u8) -> TestResult {
+        let d = ((d % 11) | 1) as usize;
+        if d == 0 {
+            return TestResult::discard();
+        }
+
+        let g: Graph<(), ()> = match heavy_square_graph(d, || (), || (), true) {
+            Ok(graph) => graph,
+            Err(_) => return TestResult::error("Bidirectional graph generation failed"),
+        };
+
+        let mut seen = HashSet::new();
+        for edge in g.edge_references() {
+            let u = edge.source().index();
+            let v = edge.target().index();
+            if u == v {
+                continue;
+            }
+            seen.insert((u.min(v), u.max(v)));
+        }
+
+        // Each edge should appear twice in bidirectional graph
+        if g.edge_count() != 2 * seen.len() {
+            return TestResult::failed();
+        }
+
+        TestResult::passed()
+    }
+
+    quickcheck(prop as fn(u8) -> TestResult);
+}
+
+#[test]
+fn prop_heavy_square_even_distance_should_fail() {
+    fn prop(d: u8) -> bool {
+        let d = (d & !1) as usize; // make d even
+        if d == 0 {
+            return true;
+        }
+        heavy_square_graph::<Graph<(), ()>, (), _, _, ()>(d, || (), || (), false).is_err()
+    }
+
+    quickcheck(prop as fn(u8) -> bool);
+}

rustworkx-core/tests/quickcheck/main.rs

@@ -6,4 +6,5 @@ mod dorogovtsev_goltsev_mendes_graph;
 mod full_rary_tree_graph;
 mod grid_graph;
 mod heavy_hex_graph;
+mod heavy_square_graph;
 mod lollipop_graph;