diff --git a/src/models.rs b/src/models.rs
index 325000a..64268af 100644
--- a/src/models.rs
+++ b/src/models.rs
@@ -203,15 +203,14 @@ mod tests {
         let (graph, vertices) = make_test_graph();
         assert_eq!(graph.vertices().count(), 10, "unexpected vertex count");
 
-        let mut vertices: Vec<Vertex> = vertices.into_iter().collect();
+        // Expects each vertex to appear exactly once.
         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");
-            }
+            assert_eq!(
+                vertices.iter().filter(|&x| *x == v).count(),
+                1,
+                "unexpected vertex {v:?} from the iterator"
+            );
         }
-        println!("vertices: {:?}", vertices);
     }
 
     #[test]
@@ -229,17 +228,22 @@ mod tests {
     fn neighbors() {
         let (graph, vertices) = make_test_graph();
         // Checks neighbors of vertex 4.
-        assert_eq!(graph.neighbors(vertices[4]).count(), 4, "unexpected vertex count");
+        assert_eq!(
+            graph.neighbors(vertices[4]).count(),
+            4,
+            "unexpected vertex count"
+        );
 
-        let mut neighbors: Vec<Vertex> = vec![vertices[1], vertices[2], vertices[7], vertices[8]];
+        // Expects each neighbor to appear exactly once. This will not work if there are multiple edges.
+        let neighbors: Vec<Vertex> = vec![vertices[1], vertices[2], vertices[7], vertices[8]];
         for v in graph.neighbors(vertices[4]) {
-            if let Some(index) = neighbors.iter().position(|&x| x == v) {
-                neighbors.swap_remove(index);
-            } else {
-                panic!("unexpected vertex of {v:?} from iterator");
-            }
+            assert_eq!(
+                neighbors.iter().filter(|&x| *x == v).count(),
+                1,
+                "unexpected neighbor {v:?} of {:?} from the iterator",
+                vertices[4]
+            );
         }
-        println!("vertices: {:?}", vertices);
     }
 
     fn make_test_graph() -> (Graph, [Vertex; 10]) {