def test_peek():
s = Stack()
s.push("apple")
s.push("banana")
actual = s.peek()
expected = "banana"
assert actual == expected
def test_stack():
stack = Stack()
with pytest.raises(InvalidOperationError) as error:
stack.peek()
assert str(error.value) == "Method not allowed on empty collection."
def test_peek_empty():
s = Stack()
with pytest.raises(InvalidOperationError) as e:
s.peek()
assert str(e.value) == "Method not allowed on empty collection"