Write a function to get the sum of a non-negative integer.
def sum_digits(n):
  if n == 0:
    return 0
  else:
    return n % 10 + sum_digits(int(n / 10))
<s>[INST]<<SYS>>Given a task and its code, generate test cases for the code.<</SYS>>Write a function to get the sum of a non-negative integer.
def sum_digits(n):
  if n == 0:
    return 0
  else:
    return n % 10 + sum_digits(int(n / 10))[/INST]assert sum_digits(345)==12
assert sum_digits(12)==3
assert sum_digits(97)==16</s>