Write a function to find the next smallest palindrome of a specified number.
import sys
def next_smallest_palindrome(num):
    numstr = str(num)
    for i in range(num+1,sys.maxsize):
        if str(i) == str(i)[::-1]:
            return i
<s>[INST]<<SYS>>Given a task and its code, generate test cases for the code.<</SYS>>Write a function to find the next smallest palindrome of a specified number.
import sys
def next_smallest_palindrome(num):
    numstr = str(num)
    for i in range(num+1,sys.maxsize):
        if str(i) == str(i)[::-1]:
            return i[/INST]assert next_smallest_palindrome(99)==101
assert next_smallest_palindrome(1221)==1331
assert next_smallest_palindrome(120)==121</s>