def test_breadth_first_traversal1():
bt = BinaryTree()
bt.root = _Node(2)
bt.root.left = _Node(7)
bt.root.right = _Node(5)
bt.root.left.left = _Node(2)
bt.root.left.right = _Node(6)
bt.root.left.right.left = _Node(5)
bt.root.left.right.right = _Node(11)
bt.root.right.right = _Node(9)
bt.root.right.right.left = _Node(4)
assert BinaryTree.breadth_first_traversal(
bt.root) == [2, 7, 5, 2, 6, 9, 5, 11, 4]
def test_breadth_first_traversal2():
bt = BinaryTree()
bt.root = _Node(2)
assert BinaryTree.breadth_first_traversal(bt.root) == [2]