def test_peek_post_dequeue():
# TODO it should return a new first value if peek is called after a dequeue
q = Queue()
q.enqueue("apples")
q.enqueue("bananas")
q.enqueue("grapes")
q.dequeue()
actual = q.peek()
expected = "bananas"
assert actual == expected
def test_exhausted():
# TODO TODO is empty should return true after dequeueing all previously queued items
q = Queue()
q.enqueue("apples")
q.enqueue("bananas")
q.enqueue("grapes")
q.dequeue()
q.dequeue()
q.dequeue()
actual = q.is_empty()
expected = True
assert actual == expected
def test_dequeue_when_full():
q = Queue()
q.enqueue("apples")
q.enqueue("bananas")
actual = q.dequeue()
expected = "apples"
assert actual == expected
def test_dequeue_when_empty():
# TODO it should raise an exception when dequeueing an empty queue
q = Queue()
with pytest.raises(InvalidOperationError) as e:
q.dequeue()
assert str(e.value) == "Method not allowed on empty collection"