def test_shift_method_returns_tail_node_data():
"""Test that the shift method of the DoublyLinkedList class returns the
tail Node's data."""
dll = DoublyLinkedList()
dll.add_node(5)
assert dll.shift() == 5
def test_add_node_method_adds_node_containing_given_data_to_list():
"""Test that the add_node method of the DoublyLinkedList class adds a Node
containing the given data to the list."""
dll = DoublyLinkedList()
dll.add_node(5)
assert dll.head.data == 5
def test_pop_method_returns_data_in_old_head_node():
"""Test that the pop method of the DoublyLinkedList class returns the data
contained in the old head Node."""
dll = DoublyLinkedList()
dll.add_node(5)
assert dll.pop() == 5
def test_display_method_returns_string():
"""Test that the display method of the DoublyLinkedList class returns a
string data type."""
dll = DoublyLinkedList()
dll.add_node(1)
assert type(dll.display()) is str
def test_add_node_method_adds_instance_of_node_to_list():
"""Test that the add_node method of the DoublyLinkedList class adds an
instance of the Node class to the list."""
dll = DoublyLinkedList()
dll.add_node(1)
assert isinstance(dll.head, Node)
def test_add_node_method_reassigns_head_and_tail_to_same_node_if_list_empty():
"""Test that the add_node method of the DoublyLinkedList class reassigns
the head and tail of the list to become the same Node if the list being
added to is empty."""
dll = DoublyLinkedList()
dll.add_node(3)
assert dll.head is dll.tail
def test_append_method_creates_instance_of_node_class_as_new_node():
"""Test that the append method of the DoublyLinkedList class adds an
instance of the Node class as the new Node in the list."""
dll = DoublyLinkedList()
dll.add_node(1)
dll.append(2)
assert isinstance(dll.tail, Node)
def test_delete_method_raises_exception_if_node_not_found():
"""Test that the delete_node method of the DoublyLinkedList class raises a
LookupError if a Node containing the given data is not found."""
dll = DoublyLinkedList()
dll.add_node(1)
with pytest.raises(LookupError):
dll.delete_node(2)
def test_shift_method_assigns_tail_node_to_none_if_list_length_is_one():
"""Test that the shift method of the DoublyLinkedList class assigns the
tail Node to become None if the list only contains one Node."""
dll = DoublyLinkedList()
dll.add_node(1)
dll.shift()
assert dll.tail is None
def test_delete_node_method_returns_string_if_deleted_node_is_tail():
"""Test that the delete_node method of the DoublyLinkedList class returns a
specific string if Node to be deleted is the tail of the list."""
dll = DoublyLinkedList()
dll.add_node(3)
dll.add_node(6)
assert dll.delete_node(3) == 'Node has been deleted.'
def test_delete_method_reassigns_head_and_tail_to_be_none_if_list_len_one():
"""Test that the delete_node method of the DoublyLinkedList class assigns
the head and tail of the list to None if the list only has one Node."""
dll = DoublyLinkedList()
dll.add_node(1)
dll.delete_node(1)
assert dll.head is None and dll.tail is None
def test_display_method_returns_accurate_representation_of_nodes_in_list():
"""Test that the display method of the DoublyLinkedList class returns an
accurate reflection of all Nodes in the list."""
dll = DoublyLinkedList()
for num in range(3):
dll.add_node(num)
assert dll.display() == 'None <- [ 2 ] <- -> [ 1 ] <- -> [ 0 ] -> None'
def test_add_node_method_properly_assigns_prev_node_pointer():
"""Test that the add_node method of the DoublyLinkedList class accurately
assigns the prev_node pointer to be the previous Node in the list."""
dll = DoublyLinkedList()
dll.add_node(10)
dll.add_node(20)
assert dll.tail.prev_node.data == 20
def test_add_node_method_properly_assigns_next_node_pointer():
"""Test that the add_node method of the DoublyLinkedList accurately assigns
the next_node pointer to be the next Node in the list."""
dll = DoublyLinkedList()
dll.add_node(1)
dll.add_node(2)
assert dll.head.next_node.data == 1
def test_pop_method_reassigns_tail_to_become_none_if_list_length_is_one():
"""Test that the pop method of the DoublyLinkedList class reassigns the
list's tail to become None if the list only contains one Node."""
dll = DoublyLinkedList()
dll.add_node(1)
dll.pop()
assert dll.tail is None
def test_append_method_correctly_reassigns_tail_to_newly_added_node():
"""Test that the append method of the DoublyLinkedList class correctly
reassigns the list's tail to become the newly appended Node."""
dll = DoublyLinkedList()
dll.add_node(1)
old_tail = dll.tail
dll.append(2)
assert dll.tail != old_tail and dll.tail.data != old_tail.data
def test_delete_node_method_returns_string_if_deleted_node_is_found():
"""Test that the delete_node method of the DoublyLinkedList class returns a
specific string if Node to be deleted is found and removed."""
dll = DoublyLinkedList()
dll.add_node(0)
dll.add_node(5)
dll.add_node(10)
assert dll.delete_node(5) == 'Node has been deleted.'
def test_shift_method_reassigns_tail_next_node_to_point_to_none():
"""Test that the shift method of the DoublyLinkedList class reassigns the
new tail's next_node pointer to None."""
dll = DoublyLinkedList()
dll.add_node(20)
dll.add_node(30)
dll.shift()
assert dll.tail.next_node is None
def test_pop_method_newly_reassigned_head_prev_node_is_none():
"""Test that the pop method of the DoublyLinkedList class assigns the
prev_node pointer of the newly reassigned head to be None."""
dll = DoublyLinkedList()
dll.add_node(5)
dll.add_node(10)
dll.pop()
assert dll.head.prev_node is None
def test_add_node_method_reassigns_tail_to_always_be_first_node_added():
"""Test that the add_node method of the DoublyLinkedList class maintains
the tail of the list properly, ensuring that no matter how many Nodes are
added that the tail is always the first Node that was added to the list."""
dll = DoublyLinkedList()
for i in range(5):
dll.add_node(i)
assert dll.tail.data == 0
def test_delete_node_method_reassigns_tail_to_be_prev_node_if_deleting_tail():
"""Test that the delete_node method of the DoublyLinkedList class correctly
reassigns the list's tail to be it's prev_node if Node to be deleted is the
list's tail."""
dll = DoublyLinkedList()
dll.add_node(30)
dll.add_node(15)
dll.delete_node(30)
assert dll.tail.data == 15
def test_append_method_assigns_new_tails_prev_node_to_be_old_tail():
"""Test that the append method of the DoublyLinkedList class assigns the
new tail's prev_node pointer to be the old tail, preserving the integrity
of the list."""
dll = DoublyLinkedList()
dll.add_node(10)
old_tail = dll.tail
dll.append(20)
assert dll.tail.prev_node is old_tail
def test_delete_node_method_reassigns_head_to_be_next_node_if_deleting_head():
"""Test that the delete_node method of the DoublyLinkedList class correctly
reassigns the list's head to be it's next_node if Node to be deleted is the
list's head."""
dll = DoublyLinkedList()
dll.add_node(1)
dll.add_node(2)
dll.delete_node(2)
assert dll.head.data == 1
def test_shift_method_reassigns_tail_and_returns_data_multiple_uses():
"""Test that the shift method of the DoublyLinkedList class correctly
reassigns the tail and returns the old tail's Node data through multiple
uses."""
dll = DoublyLinkedList()
for num in range(10):
dll.add_node(num)
for _ in range(10):
old_tail = dll.tail
assert dll.shift() == old_tail.data and dll.tail is not old_tail
def test_delete_node_method_removes_node_with_prev_and_next_pointers():
"""Test that the delete_node method of the DoublyLinkedList class
successfully removes a Node with prev_node and next_node pointers actively
pointing to other Nodes."""
dll = DoublyLinkedList()
for i in range(3):
dll.add_node(i)
dll.delete_node(2)
assert dll.head.next_node.data != 2 and dll.tail.prev_node.data != 2
def test_pop_method_reassigns_head_to_become_next_node():
"""Test that the pop method of the DoublyLinkedList class correctly
reassigns the head to become it's next_node if the list contains more than
one Node."""
dll = DoublyLinkedList()
dll.add_node(3)
dll.add_node(6)
head_next_node = dll.head.next_node
dll.pop()
assert dll.head is head_next_node
def test_shift_method_reassigns_tail_to_become_prev_node():
"""Test that the shift method of the DoublyLinkedList class correctly
reassigns the tail Node to become it's prev_node pointer if the list
contains more than two Nodes."""
dll = DoublyLinkedList()
dll.add_node(1)
dll.add_node(2)
tail_prev_node = dll.tail.prev_node
dll.shift()
assert dll.tail is tail_prev_node
def test_pop_method_correctly_reassigns_head_and_returns_data_multiple_uses():
"""Test that the pop method of the DoublyLinkedList class correctly
reassigns the head and returns the old head's data after multiple uses."""
dll = DoublyLinkedList()
for num in range(10):
dll.add_node(num)
for _ in range(10):
old_head = dll.head
assert dll.pop() == old_head.data and dll.head is not old_head
