我测试了好多遍也错，明明和老师写的一样呀：

log = print

def ensure(condition, message):
    if condition:
        log('*** 测试成功')
    else:
        log('*** 测试失败:', message)

def sum(number_list):
    r = 0
    for e in number_list:
        log(e)
        r = r + e
    return r

def minus(number_list):
    r = number_list[0]
    for i in range(1, len(number_list)):
        r = r - number_list[i]
    return r

def product(number_list):
    r = 1
    for e in number_list:
        r = r * e
    return r

def divide(number_list):
    r = number_list[0]
    for i in range(1, len(number_list)):
        r = r / number_list[i]
    return r

def apply_list(op, number_list):
    if op == '+':
        r = sum(number_list)
        return r
    elif op == '-':
        r = minus(number_list)
        return r
    elif op == '*':
        r = product(number_list)
        return r
    elif op == '/':
        r = divide(number_list)
        return r

def test_apply_list():
    ensure(apply_list('+', [1, 2, 3, 4]) == 10, 'apply list 111')
    ensure(apply_list('-', [1, 2, 3, 4]) == -8, 'apply list 222')
    ensure(apply_list('*', [1, 2, 3, 4]) == 24, 'apply list 333')
    ensure(apply_list('/', [12, 2, 3]) == 2, 'apply list 444')
    log('$$$ apply_list 测试完成')

test_apply_list()

求求大佬帮帮我找一下哪里错