public void IndexMinPQ_Enqueue()
    {
        var q = new IndexPriorityQueue<int>();
        var minItem = int.MaxValue;

        for (int i = 0; i < items.Length; i++)
        {
            // After adding each item, the min item should be on top
            q.Enqueue(i, items[i]);
            minItem = Math.Min(items[i], minItem);

            Assert.IsTrue(q.Contains(i));
            Assert.AreEqual(q.MinKey(), minItem);
        }
    }