public void BinarySearchTreePositiveTest()
{
var bst = new BinarySearchTree<int, string>();
bst.Add(10, "Mr. and Mrs. Iqbal Ahmed Mughal");
bst.Add(1, "Sana");
bst.Add(2, "Mehwish");
bst.Add(3, "Adil");
bst.Add(4, "Ammara");
Assert.AreEqual("Ammara", bst.Retrieve(4));
}