def test_delete_root_node_two_children(self):
"""Test to ensure the delete method correctly
deletes a root node that has two children.
"""
#Tree should look like this
# 23
# 12 34
# 9 15 45
# 8 56
bst = BinarySearchTree()
self.assertEqual(bst.size, 0)
self.assertEqual(bst.get_height(), -1)
nodes = [23, 12, 34, 9, 15, 45, 56, 8]
#add nodes
for node in nodes:
bst.insert(node)
self.assertEqual(bst.size, 8)
self.assertEqual(bst.get_height(), 3)
bst.delete(23)
self.assertEqual(bst.size, 7)
self.assertEqual(bst.get_height(), 3)
self.assertIsNone(bst.search(23))
self.assertEqual(bst.root.data, 34)
def test_delete_root_node_left_child(self):
"""Test to delete a root node with only one child
that is the left child.
"""
#Tree should look like this
# 56
# 45
# 34
# 23
bst = BinarySearchTree()
self.assertEqual(bst.size, 0)
self.assertEqual(bst.get_height(), -1)
nodes = [56, 45, 34, 23]
#add nodes
for node in nodes:
bst.insert(node)
self.assertEqual(bst.size, 4)
self.assertEqual(bst.get_height(), 3)
#root has only a right child
bst.delete(56)
self.assertEqual(bst.size, 3)
self.assertEqual(bst.get_height(), 2)
self.assertIsNone(bst.search(56))
self.assertEqual(bst.root.data, 45)
def test_delete_node_one_child(self):
"""Test to delete a node that has only one child."""
#Tree should look like this
# 23
# 12 34
# 9 15 45
# 8 56
bst = BinarySearchTree()
self.assertEqual(bst.size, 0)
self.assertEqual(bst.get_height(), -1)
nodes = [23, 12, 34, 9, 15, 45, 56, 8]
#add nodes
for node in nodes:
bst.insert(node)
self.assertEqual(bst.size, 8)
self.assertEqual(bst.get_height(), 3)
#delete node that just has a left child
bst.delete(9)
self.assertEqual(bst.size, 7)
self.assertEqual(bst.get_height(), 3)
self.assertIsNone(bst.search(9))
#delete node that just has a right child
bst.delete(45)
self.assertEqual(bst.size, 6)
self.assertEqual(bst.get_height(), 2)
self.assertIsNone(bst.search(45))
def test_delete_leaf_node(self):
"""Test that the delete method functions correctly
when deleting a leaf node.
"""
#Tree should look like this
# 23
# 12 34
# 9 15 45
# 56
bst = BinarySearchTree()
self.assertEqual(bst.size, 0)
self.assertEqual(bst.get_height(), -1)
nodes = [23, 12, 34, 9, 15, 45, 56]
#add nodes
for node in nodes:
bst.insert(node)
self.assertEqual(bst.size, 7)
self.assertEqual(bst.get_height(), 3)
#Case 1: Deleting a leaf node
bst.delete(56)
self.assertEqual(bst.size, 6)
self.assertEqual(bst.get_height(), 2)
self.assertIsNone(bst.search(7))
def test_delete_node_not_in_tree(self):
"""Test to ensure that the tree isn't altered if the
delete method is called and the node doesn't exist
"""
#Tree should look like this
# 23
# 12 34
# 9 15 45
# 56
bst = BinarySearchTree()
self.assertEqual(bst.size, 0)
self.assertEqual(bst.get_height(), -1)
nodes = [23, 12, 34, 9, 15, 45, 56]
#add nodes
for node in nodes:
bst.insert(node)
self.assertEqual(bst.size, 7)
self.assertEqual(bst.get_height(), 3)
#try deleting a node that doesn't exist
self.assertEqual(bst.get_height(), 3)
bst.delete(145)
self.assertEqual(bst.size, 7)
self.assertEqual(bst.get_height(), 3)
def test_delete_node_from_empty_tree(self):
"""Test to ensure that the tree isn't altered if the
delete method is called when the tree is empty.
"""
bst = BinarySearchTree()
self.assertEqual(bst.size, 0)
self.assertEqual(bst.get_height(), -1)
bst.delete(12)
self.assertEqual(bst.size, 0)
def test_delete_root_as_leaf(self):
"""Test to ensure that the delete method works properly
when the root is the only node in the tree.
"""
bst = BinarySearchTree()
self.assertEqual(bst.size, 0)
self.assertEqual(bst.get_height(), -1)
bst.insert(12)
self.assertEqual(bst.size, 1)
self.assertEqual(bst.get_height(), 0)
root = bst.search(12)
self.assertEqual(root.data, 12)
bst.delete(12)
self.assertEqual(bst.size, 0)
self.assertEqual(bst.get_height(), -1)
self.assertIsNone(bst.root)
def test_delete_node_two_children(self):
"""Test to delete a node with two children."""
#Tree should look like this
# 23
# 12 34
# 9 15 45
# 8 56
bst = BinarySearchTree()
self.assertEqual(bst.size, 0)
self.assertEqual(bst.get_height(), -1)
nodes = [23, 12, 34, 9, 15, 45, 56, 8]
#add nodes
for node in nodes:
bst.insert(node)
self.assertEqual(bst.size, 8)
self.assertEqual(bst.get_height(), 3)
bst.delete(12)
self.assertEqual(bst.size, 7)
self.assertEqual(bst.get_height(), 3)
self.assertIsNone(bst.search(12))