def test_peek(create_pq):
"""Ensures that peek raises an error when the priority queue
is empty, and that it returns the right value when items are added.
"""
pq = PriorityQueue()
with pytest.raises(IndexError):
pq.peek()
pq = create_pq
pq.insert(100, "This is so much fun!")
assert pq.peek() == "This is so much fun!"
assert pq.peek() != "This sucks"
