def test_insert_head():
    ll = DoublyLinkedList()
    for i in range(ITERS):
        ll.insert_head(i)
        assert (len(ll) == i + 1)
        assert (ll.peek_head() == i)
def test_ll_equality():
    ll1, ll2 = DoublyLinkedList(), DoublyLinkedList()
    for i in range(ITERS):
        ll1.insert_head(i)
        ll2.insert_head(i)
    assert (ll1 == ll2)