def test_prepend(self):
ll = LinkedList()
# Prepend should always update head node
ll.prepend('C')
assert ll.head.data == 'C' # New head
assert ll.tail.data == 'C' # New head
ll.prepend('B')
assert ll.head.data == 'B' # New head
assert ll.tail.data == 'C' # Unchanged
ll.prepend('A')
assert ll.head.data == 'A' # New head
assert ll.tail.data == 'C' # Unchanged
def test_append(self):
ll = LinkedList()
# Append should always update tail node
ll.append('A')
assert ll.head.data == 'A' # New head
assert ll.tail.data == 'A' # New tail
ll.append('B')
assert ll.head.data == 'A' # Unchanged
assert ll.tail.data == 'B' # New tail
ll.append('C')
assert ll.head.data == 'A' # Unchanged
assert ll.tail.data == 'C' # New tail
def test_length_after_delete(self):
ll = LinkedList(['A', 'B', 'C', 'D', 'E'])
assert ll.length() == 5
# Delete should decrease length
ll.delete('A')
assert ll.length() == 4
ll.delete('E')
assert ll.length() == 3
ll.delete('C')
assert ll.length() == 2
ll.delete('D')
assert ll.length() == 1
ll.delete('B')
assert ll.length() == 0
def test_length_after_append_and_prepend(self):
ll = LinkedList()
assert ll.length() == 0
# Append and prepend should increase length
ll.append('C')
assert ll.length() == 1
ll.prepend('B')
assert ll.length() == 2
ll.append('D')
assert ll.length() == 3
ll.prepend('A')
assert ll.length() == 4
def test_length_after_prepend(self):
ll = LinkedList()
assert ll.length() == 0
# Prepend should increase length
ll.prepend('C')
assert ll.length() == 1
ll.prepend('B')
assert ll.length() == 2
ll.prepend('A')
assert ll.length() == 3
def test_items_after_prepend(self):
ll = LinkedList()
assert ll.items() == []
# Prepend should add new item to head of list
ll.prepend('C')
assert ll.items() == ['C']
ll.prepend('B')
assert ll.items() == ['B', 'C']
ll.prepend('A')
assert ll.items() == ['A', 'B', 'C']
def test_items_after_append(self):
ll = LinkedList()
assert ll.items() == []
# Append should add new item to tail of list
ll.append('A')
assert ll.items() == ['A']
ll.append('B')
assert ll.items() == ['A', 'B']
ll.append('C')
assert ll.items() == ['A', 'B', 'C']
def test_init_with_list(self):
ll = LinkedList(['A', 'B', 'C'])
# Initializer should append items in order
assert ll.head.data == 'A' # First item
assert ll.tail.data == 'C' # Last item
def test_init(self):
ll = LinkedList()
# Initializer should add instance properties
assert ll.head is None # First node
assert ll.tail is None # Last node
def test_delete_with_item_not_in_list(self):
ll = LinkedList(['A', 'B', 'C'])
# Delete should raise error if item not found
with self.assertRaises(ValueError):
ll.delete('X') # Item not found in list
def test_delete_with_5_items(self):
ll = LinkedList(['A', 'B', 'C', 'D', 'E'])
assert ll.head.data == 'A' # First item
assert ll.tail.data == 'E' # Last item
ll.delete('A')
assert ll.head.data == 'B' # New head
assert ll.tail.data == 'E' # Unchanged
ll.delete('E')
assert ll.head.data == 'B' # Unchanged
assert ll.tail.data == 'D' # New tail
ll.delete('C')
assert ll.head.data == 'B' # Unchanged
assert ll.tail.data == 'D' # Unchanged
ll.delete('D')
assert ll.head.data == 'B' # Unchanged
assert ll.tail.data == 'B' # New tail
ll.delete('B')
assert ll.head is None # No head
assert ll.tail is None # No tail
def test_delete_with_3_items(self):
ll = LinkedList(['A', 'B', 'C'])
assert ll.head.data == 'A' # First item
assert ll.tail.data == 'C' # Last item
ll.delete('A')
assert ll.head.data == 'B' # New head
assert ll.tail.data == 'C' # Unchanged
ll.delete('C')
assert ll.head.data == 'B' # Unchanged
assert ll.tail.data == 'B' # New tail
ll.delete('B')
assert ll.head is None # No head
assert ll.tail is None # No tail
# Delete should raise error if item was already deleted
with self.assertRaises(ValueError):
ll.delete('A') # Item no longer in list
with self.assertRaises(ValueError):
ll.delete('B') # Item no longer in list
with self.assertRaises(ValueError):
ll.delete('C') # Item no longer in list
def test_find(self):
ll = LinkedList(['A', 'B', 'C'])
assert ll.find(lambda item: item == 'B') == 'B' # Match equality
assert ll.find(lambda item: item < 'B') == 'A' # Match less than
assert ll.find(lambda item: item > 'B') == 'C' # Match greater than
assert ll.find(lambda item: item == 'X') is None # No matching item