public void CorrectKeyReturned() { //Arrange int[] elements = new int[] { 1, -5, 24, 561, -300, 15, 36, 82, 4, 50 }; BinarySearchTreeSet <int> bst = new BinarySearchTreeSet <int>(); foreach (int el in elements) { bst.Insert(el); } //Act & Assert var sortedElements = elements.OrderBy(x => x).ToArray(); for (int i = 0; i < sortedElements.Length; i++) { var currentElement = sortedElements[i]; int selectedElement = bst.Select(i); Assert.Equal(currentElement, selectedElement); } }