Adding quickcheck for star graph (#1486)

Checking the number of nodes, edges, no self loops and all the edges pass through the central node.

Author: Krishn1412

rustworkx-core/tests/quickcheck/main.rs

@@ -12,3 +12,4 @@ mod karate_club;
 mod lollipop_graph;
 mod path_graph;
 mod petersen_graph;
+mod star_graph;

rustworkx-core/tests/quickcheck/star_graph.rs

@@ -0,0 +1,56 @@
+#[cfg(test)]
+mod tests {
+    use petgraph::graph::DiGraph;
+    use petgraph::visit::EdgeRef;
+    use quickcheck::{quickcheck, TestResult};
+
+    use rustworkx_core::generators::star_graph;
+
+    #[test]
+    fn prop_star_graph_structure() {
+        fn prop(n: usize, bidirectional: bool, inward: bool) -> TestResult {
+            let n = n % 50; // prevent overly large graphs
+
+            let g: DiGraph<(), ()> =
+                match star_graph(Some(n), None, || (), || (), inward, bidirectional) {
+                    Ok(graph) => graph,
+                    Err(_) => return TestResult::failed(),
+                };
+
+            // Number of nodes should be exactly n
+            if g.node_count() != n {
+                return TestResult::failed();
+            }
+
+            // Star graph has one central node (0), all others connected to/from it
+            let expected_edge_count = if n < 2 {
+                0
+            } else if bidirectional {
+                2 * (n - 1)
+            } else {
+                n - 1
+            };
+            if g.edge_count() != expected_edge_count {
+                return TestResult::failed();
+            }
+
+            // No self-loops
+            if g.edge_references().any(|e| e.source() == e.target()) {
+                return TestResult::failed();
+            }
+
+            // All edges must involve the center node (index 0)
+            for edge in g.edge_references() {
+                let src = edge.source().index();
+                let dst = edge.target().index();
+                if src != 0 && dst != 0 {
+                    return TestResult::failed();
+                }
+            }
+
+            TestResult::passed()
+        }
+
+        quickcheck(prop as fn(usize, bool, bool) -> TestResult);
+    }
+}