def test_delete_at_head__non_empty_list_with_one_element__ok(self):
alist = LinkedList(Node(1))
assert str(alist) == "1 -> None"
assert alist.get_head().data == 1
alist.delete_at_head()
assert alist.is_empty() is True
assert alist.get_head() is None
def test_delete_at_head__empty_list__ok(self):
alist = LinkedList()
assert alist.is_empty() is True
assert alist.get_head() is None
alist.delete_at_head()
assert alist.is_empty() is True
assert alist.get_head() is None
def test_delete_at_head__empty_list_with_many_elements__ok(self):
alist = LinkedList()
for i in range(1, 4):
alist.insert_at_head(i)
assert str(alist) == "3 -> 2 -> 1 -> None"
assert alist.get_head().data == 3
alist.delete_at_head()
assert str(alist) == "2 -> 1 -> None"
assert alist.get_head().data == 2