def test_peek_empty_queue():
queue = PriorityQueue()
with pytest.raises(IndexError) as exc:
queue.peek()
assert str(exc.value) == "peek from empty priority queue"
def test_enqueue(items, expected_head):
queue = PriorityQueue()
for item in items:
queue.enqueue(item)
assert len(queue) == len(items)
assert queue.peek() == expected_head
def test_peek():
queue = PriorityQueue()
queue.enqueue("a")
queue.enqueue("b")
assert queue.peek() == "b"
assert len(queue) == 2
