def test_return_postorder_traversal():
bst = BinarySearchTree()
bst.add(3)
bst.add(2)
bst.add(6)
actual = bst.post_order()
expected = [2, 6, 3]
assert actual == expected
def test_return_inorder_traversal():
bst = BinarySearchTree()
bst.add(3)
bst.add(2)
bst.add(6)
actual = bst.in_order()
expected = [2, 3, 6]
assert actual == expected
def test_return_preorder_traversal():
bst = BinarySearchTree()
bst.add(3)
bst.add(2)
bst.add(6)
actual = bst.pre_order()
expected = [3, 2, 6]
assert actual == expected
def test_add_to_right():
bst = BinarySearchTree()
bst.add(3)
bst.add(2)
bst.add(6)
assert bst.root.right.value == 6
def test_instantiate_single_root():
bst = BinarySearchTree()
bst.add(1)
assert bst.root.value == 1