public void SkipListAddTest()
{
var skiplist = new Skiplist <int>();
skiplist.Add(5);
skiplist.Add(50);
var str = skiplist.ToString();
skiplist.Add(500);
skiplist.Add(5000);
skiplist.Add(51);
skiplist.Add(501);
Assert.AreEqual("0 5 50 51 500 501 5000 0 ", skiplist.ToString());
}