Adding Quickcheck for binomial tree graph. (#1470)

The quickcheck verifies the structure of binomial tree graph by checking number of node, number of edges and if they are bidirectional.

I plan on adding quickchecks for all the deterministic graph generators and some other algos like bipartite colouring before moving forward.

Author: Krishn1412

rustworkx-core/tests/quickcheck/binomial_tree_graph.rs

@@ -0,0 +1,46 @@
+use petgraph::graph::UnGraph;
+use petgraph::visit::EdgeRef;
+use quickcheck::{quickcheck, TestResult};
+use rustworkx_core::generators::binomial_tree_graph;
+
+#[test]
+fn prop_binomial_tree_structure() {
+    fn prop(order: u32) -> TestResult {
+        let order = order % 10; // upto 2^10 nodes due to memory constraints.
+        if order >= 60 {
+            return TestResult::discard();
+        }
+
+        let g = match binomial_tree_graph::<UnGraph<(), ()>, (), _, _, ()>(
+            order,
+            None,
+            || (),
+            || (),
+            true,
+        ) {
+            Ok(g) => g,
+            Err(_) => return TestResult::error("Unexpected error in graph generation"),
+        };
+
+        let expected_nodes = 2_usize.pow(order);
+        let expected_edges = 2 * (expected_nodes - 1);
+
+        if g.node_count() != expected_nodes || g.edge_count() != expected_edges {
+            return TestResult::failed();
+        }
+
+        // Check that for every edge, a reverse edge exists
+        for edge in g.edge_references() {
+            let u = edge.source();
+            let v = edge.target();
+            let reverse_exists = g.find_edge(v, u).is_some();
+            if !reverse_exists {
+                return TestResult::failed();
+            }
+        }
+
+        TestResult::passed()
+    }
+
+    quickcheck(prop as fn(u32) -> TestResult);
+}

rustworkx-core/tests/quickcheck/main.rs

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