def test_find_prefix_returns_None_when_no_children_have_the_prefix(self):
"""Verify we receive None from find_prefix for missing children."""
node = trie.TrieNode(
'E',
'E is for Eat',
children={'a': trie.TrieNode('a', 'a is for Apple')})
assert node.find_prefix('b') is None
def test_find_prefix(self):
"""Verify we can find a child with the specified prefix."""
node = trie.TrieNode(
'E',
'E is for Eat',
children={'a': trie.TrieNode('a', 'a is for Apple')})
child = node.find_prefix('a')
assert child is not None
assert child.prefix == 'a'
assert child.data == 'a is for Apple'
def test_add_child_overrides_previous_child(self):
"""Verify adding a child will replace the previous child."""
node = trie.TrieNode(
'E',
'E is for Eat',
children={'a': trie.TrieNode('a', 'a is for Apple')})
previous = node.find_prefix('a')
assert previous is not None
added = node.add_child('a', 'a is for Ascertain')
assert node.find_prefix('a') is added
def test_traverse(self):
"""Verify traversal is depth-first and pre-order."""
root = trie.TrieNode(None, None)
node = root.add_child('A', 'A')
root.add_child('a', 'a')
node.add_child('B', 'B')
node = node.add_child('b', 'b')
node.add_child('C', 'C')
node.add_child('c', 'c')
# The sub-tree here should look something like
#
# <root>
# / \
# A a
# / |
# B b
# / \
# C c
#
# And the traversal should look like:
#
# A B b C c a
expected_order = ['A', 'B', 'b', 'C', 'c', 'a']
for expected, actual_node in zip(expected_order, root.traverse()):
assert actual_node.prefix == expected
def test_traverse_does_nothing_when_a_node_has_no_children(self):
"""Verify traversing a node with no children does nothing."""
node = trie.TrieNode('E', 'E is for Eat')
assert list(node.traverse()) == []
def test_add_child(self):
"""Verify we add children appropriately."""
node = trie.TrieNode('E', 'E is for Eat')
assert node.find_prefix('a') is None
added = node.add_child('a', 'a is for Apple')
assert node.find_prefix('a') is added