def test_delete_before():
head1 = DoublyLinkedListNode(0)
node11 = DoublyLinkedListNode(1, prev=head1)
node12 = DoublyLinkedListNode(2, prev=node11)
head1.next = node11
node11.next = node12
head2 = DoublyLinkedListNode(0)
node21 = DoublyLinkedListNode(2, prev=head2)
head2.next = node21
assert not is_same(head1, head2)
delete_before(node12)
assert is_same(head1, head2)
def test_nontrivial_insert_after():
head1 = DoublyLinkedListNode(0)
node11 = DoublyLinkedListNode(1, prev=head1)
node12 = DoublyLinkedListNode(2, prev=node11)
head1.next = node11
node11.next = node12
head2 = DoublyLinkedListNode(0)
node21 = DoublyLinkedListNode(2, prev=head2)
head2.next = node21
assert not is_same(head1, head2)
insert_after(head2, 1)
assert is_same(head1, head2)
def test_trivial_insert_before():
head1 = DoublyLinkedListNode(1)
insert_before(head1, 0)
head2 = DoublyLinkedListNode(0)
node2 = DoublyLinkedListNode(1)
head2.next = node2
node2.prev = head2
assert is_same(head1.prev, head2)
def test_trivial_insert_after():
head1 = DoublyLinkedListNode(0)
insert_after(head1, 1)
head2 = DoublyLinkedListNode(0)
node2 = DoublyLinkedListNode(1)
head2.next = node2
node2.prev = head2
assert is_same(head1, head2)
def test_nontrivial_false():
head1 = DoublyLinkedListNode(0)
node11 = DoublyLinkedListNode(1, prev=head1)
node12 = DoublyLinkedListNode(2, prev=node11)
head1.next = node11
node11.next = node12
head2 = DoublyLinkedListNode(0)
node21 = DoublyLinkedListNode(1, prev=head1)
node22 = DoublyLinkedListNode(2, prev=head1) # wrong prev
head2.next = node21
node21.next = node22
assert not is_same(head1, head2)
def test_trivial_true():
head1 = DoublyLinkedListNode(0)
head2 = DoublyLinkedListNode(0)
assert is_same(head1, head2)
def test_trivial():
assert is_same(None, None)
def test_trivial_false():
head1 = DoublyLinkedListNode(0)
head2 = DoublyLinkedListNode(1)
assert not is_same(head1, head2)