Adding quickcheck for karate club (#1483)

Added quick to check the structural property of karate_club_graph, by ensuring the number of nodes, edges, there are no self loops and all nodes referenced are valid.

Author: Krishn1412

rustworkx-core/tests/quickcheck/karate_club.rs

@@ -0,0 +1,45 @@
+#[cfg(test)]
+mod tests {
+    use petgraph::graph::UnGraph;
+    use petgraph::visit::EdgeRef;
+    use quickcheck::{quickcheck, TestResult};
+
+    use rustworkx_core::generators::karate_club_graph;
+
+    #[test]
+    fn prop_karate_club_basic_structure() {
+        fn prop(x: u8, y: u16) -> TestResult {
+            let g: UnGraph<u8, u16> = karate_club_graph(
+                |is_hi| if is_hi { x } else { x.wrapping_add(1) },
+                |strength| y.wrapping_add(strength as u16),
+            );
+
+            // Always 34 nodes
+            if g.node_count() != 34 {
+                return TestResult::failed();
+            }
+
+            // Always 78 edges
+            if g.edge_count() != 78 {
+                return TestResult::failed();
+            }
+
+            // No self-loops
+            if g.edge_references().any(|e| e.source() == e.target()) {
+                return TestResult::failed();
+            }
+
+            // All nodes referenced are valid
+            let max_node = g.node_count();
+            for edge in g.edge_references() {
+                if edge.source().index() >= max_node || edge.target().index() >= max_node {
+                    return TestResult::failed();
+                }
+            }
+
+            TestResult::passed()
+        }
+
+        quickcheck(prop as fn(u8, u16) -> TestResult);
+    }
+}

rustworkx-core/tests/quickcheck/main.rs

@@ -8,4 +8,5 @@ mod grid_graph;
 mod heavy_hex_graph;
 mod heavy_square_graph;
 mod hexagonal_lattice_graph;
+mod karate_club;
 mod lollipop_graph;