def test_min_stack():
stack = Stack()
stack.push(50)
stack.push(100)
stack.push(10)
stack.push(30)
expected = 10
actual = stack.min()
assert actual == expected, 'Error on test_min_stack.'
def test_min_stack_large():
stack = Stack()
stack.push(50)
stack.push(100)
stack.push(1000)
stack.push(30)
stack.push(150)
stack.push(250)
stack.push(5)
stack.push(500)
stack.pop()
stack.pop()
stack.pop()
stack.pop()
stack.pop()
expected = 50
actual = stack.min()
assert actual == expected, 'Error on test_min_stack_large.'