log=print
def product(number_list):
    r=1
    for i in range(len(number_list)):
        n=number_list[i]
        r=r*n
    return r
def ensure(condition, message):
    if condition:
        log('*** 测试成功')
    else:
        log('*** 测试失败:', message)
def test_product():
    numbers = [1, 2, 3, 4]
    result = 24
    ensure(product(numbers) == result, 'error product 1')
    ensure(product([0, 7, 9]) == 0, 'error product 2')
    ensure(product([]) == 1, 'error product 3')
    log('$$$ product 测试完成')
test_product()

为什么你们发代码都要横着发？

log = print
def ensure(condition, message):
    if condition:
        log('*** 测试成功')
    else:
        log('*** 测试失败:', message)
def product(number_list):
    s = 1
    for i in range(len(number_list)):
        n = number_list[i]
        s = s * n
    return s

def test_product():
    numbers = [1, 2, 3, 4]
    result = 24
    ensure(product(numbers) == result, 'error product 1')
    ensure(product([0, 7, 9]) == 0, 'error product 2')
    ensure(product([]) == 1, 'error product 3')
    log('$$$ product 测试完成')

test_product()

总结一下，你ensure函数没放进去； log = print 也没放进去。