def test_erase_head():
l = SingleLinkedList()
l.push_front(1)
assert l.head.data == 1
l.erase(0)
assert l.head == None
def test_erase_middle():
l = SingleLinkedList()
l.push_back(1)
l.push_back(2)
l.push_back(3)
assert l.head.next.data == 2
l.erase(1)
assert l.head.next.data == 3
def test_erase_tail():
l = SingleLinkedList()
l.push_back(1)
assert l.tail.data == 1
l.push_back(2)
assert l.tail.data == 2
l.push_back(3)
assert l.tail.data == 3
l.erase(2)
assert l.tail.data == 2