def test_tree_preorder():
bt = BinaryTree()
bt.root = Node(6)
bt.root.right = Node(5)
bt.root.left = Node(-1)
bt.root.right.left = Node(7)
bt.root.left.left = Node(10)
bt.root.right.right = Node(3)
assert bt.preOrder() == [6, -1, 10, 5, 7, 3]
def test_tree_single_left_right():
bt = BinaryTree()
bt.root = Node(7)
bt.root.left = Node(3)
bt.root.right = Node(2)
assert bt.root.value == 7
assert bt.root.left.value == 3
assert bt.root.right.value == 2
assert bt.preOrder() == [7, 3, 2]