def test_stack_peek():
stack = Stack()
stack.push(7)
stack.push(3)
assert stack.peek() == 3
def test_stack_empty_exception():
stack = Stack()
with pytest.raises(Exception):
assert stack.pop()
with pytest.raises(Exception):
assert stack.peek()
def test_peek_S():
nums = Stack()
nums.push(1)
nums.push(2)
expected = 2
assert expected == nums.peek()