def test_depth_one():
"""Test that a node of one returns a depth of one."""
from bst import Node
a = Node(1)
assert a.depth() == 1
def test_depth_many():
"""Test that a node with one extra on the left has a depth of 2."""
from bst import Node
a = Node(20)
a.left = Node(16)
assert a.depth() == 2
def test_depth_none():
"""Test that a node of nothing returns a value of nothing."""
from bst import Node
a = Node()
assert a.depth() == 0
