def test_in_order_three():
tree = BinarySearchTree()
tree.add(5)
tree.add(3)
tree.add(15)
expected = [3, 5, 15]
actual = tree.in_order()
assert actual == expected
def test_in_order_more():
tree = BinarySearchTree()
tree.add(20)
tree.add(5)
tree.add(10)
tree.add(15)
tree.add(25)
tree.add(35)
tree.add(40)
tree.add(23)
tree.add(45)
expected = [5, 10, 15, 20, 23, 25, 35, 40, 45]
actual = tree.in_order()
assert actual == expected