def test_linked_list_insert_before():
ll = LinkedList()
ll.head = Node(1)
ll.head.next = Node(2)
ll.insert_before(2, 3)
assert ll.head.next.value == 3
assert ll.head.next.next.value == 2
def test_linked_list_insert_before():
"""Test a new value can be inserted before a value already in the linked list."""
linked_list = LinkedList()
value = 1
linked_list.insert(value)
new_value = 2
linked_list.insert_before(value, new_value)
assert linked_list.head.value == new_value
assert linked_list.head.next.value == value
newer_value = 3
linked_list.insert_before(value, newer_value)
assert linked_list.head.next.value == newer_value
assert linked_list.head.next.next.value == value