def test_delete_from_empty_trie(self):
"""
If string cannot be found, a ValueError is raised.
"""
# Make the tree
tree = PrefixTree()
# raise Exception
with self.assertRaises(ValueError):
tree.delete('CS Rocks!')
def test_delete_key_shares_prefix_with_other_strings(self):
"""
A string is deleted from the trie without removing strings that contain
the same prefix.
"""
# Make the tree
input = ['ABC', 'ABD', 'A', 'XYZ', "WAFFLE TIME"]
tree = PrefixTree(input)
# Remove a string who shares letters with other strings
tree.delete('A')
# test the length of trie is adjusted correctly
assert tree.size == len(input) - 1
# test all the other strings with common nodes can still be found
assert tree.contains('ABC') is True
assert tree.contains('ABD') is True
# test that the deleted string cannot be found
assert tree.contains('A') is False
