Add tests for Graph::vertices()

src/models.rs

@@ -188,6 +188,32 @@ mod tests {
         }
     }
 
+    #[test]
+    fn vertices_empty() {
+        let graph = Graph::new();
+        assert_eq!(
+            graph.vertices().count(),
+            0,
+            "vertex iterator of empty graph should have no elements"
+        );
+    }
+
+    #[test]
+    fn vertices() {
+        let (graph, vertices) = make_test_graph();
+        assert_eq!(graph.vertices().count(), 10, "unexpected vertex count");
+
+        let mut vertices: Vec<Vertex> = vertices.into_iter().collect();
+        for v in graph.vertices() {
+            if let Some(index) = vertices.iter().position(|&x| x == v) {
+                vertices.swap_remove(index);
+            } else {
+                panic!("unexpected vertex of {v:?} from iterator");
+            }
+        }
+        println!("vertices: {:?}", vertices);
+    }
+
     fn make_test_graph() -> (Graph, [Vertex; 10]) {
         let mut graph = Graph::new();
         let vertices: [Vertex; 10] = core::array::from_fn(|_| graph.add_vertex());