def test_BST_pre_order():
bst = BinarySearchTree()
bst.add(1)
bst.add(3)
bst.add(20)
bst.add(7)
bst.add(8)
actual = bst.pre_order()
expected = [1, 3, 20, 7, 8]
assert actual == expected
def test_pre():
bst = BinarySearchTree()
bst.add(1)
bst.add(2)
bst.add(3)
bst.add(4)
bst.add(5)
actual = bst.pre_order()
expected = [1, 2, 3, 4, 5]
assert actual == expected
def test_BST_pre_order_2():
bst = BinarySearchTree()
bst.add(5)
bst.add(7)
bst.add(8)
bst.add(6)
bst.add(3)
bst.add(2)
bst.add(4)
actual = bst.pre_order()
expected = [5, 3, 2, 4, 7, 6, 8]
assert actual == expected