def test_prev_node_of_min(self):
"""
test the following binary search tree
1
\
2
\
3 <-- get next node of 3
"""
bst = BinarySearchTree()
bst.insert(1)
bst.insert(2)
node = bst.insert(3)
self.assertEqual(bst.next(node), None)
def test_next_node_has_right_subtree(self):
"""
test the following binary search tree
1 <-- get next node of 1
\
3
/ \
2 4
"""
bst = BinarySearchTree()
node = bst.insert(1)
bst.insert(3)
expected_next = bst.insert(2)
bst.insert(4)
self.assertEqual(bst.next(node), expected_next)