def mul(x, *y):

    result=x

    for n in y:

            result *=n

    return result

print('mul(5) =', mul(5))

print('mul(5, 6) =', mul(5, 6))

print('mul(5, 6, 7) =', mul(5, 6, 7))

print('mul(5, 6, 7, 9) =', mul(5, 6, 7, 9))

if mul(5) != 5:

    print('测试失败!')

elif mul(5, 6) != 30:

    print('测试失败!')

elif mul(5, 6, 7) != 210:

    print('测试失败!')

elif mul(5, 6, 7, 9) != 1890:

    print('测试失败!')

else:

    try:

        mul()

        print('测试失败!')

    except TypeError:

        print('测试成功!')