diff --git a/tests/pure_binary_heap.rs b/tests/pure_binary_heap.rs
index 9daeaff..1971127 100644
--- a/tests/pure_binary_heap.rs
+++ b/tests/pure_binary_heap.rs
@@ -9,6 +9,7 @@ mod tests {
         heap.add(-3);
         heap.add(6);
         heap.add(1);
+        assert_eq!(heap.len(), 4);
         assert_eq!(heap.pop(), Some(-3));
         assert_eq!(heap.pop(), Some(1));
         assert_eq!(heap.pop(), Some(4));
@@ -19,6 +20,7 @@ mod tests {
     #[test]
     fn test_pure_binary_heap_from_iter() {
         let mut heap = BinaryHeap::from_iter(vec![7, 3, 6, 9]);
+        assert_eq!(heap.len(), 4);
         assert_eq!(heap.pop(), Some(3));
         assert_eq!(heap.pop(), Some(6));
         assert_eq!(heap.pop(), Some(7));