Write a python function to find the sum of the largest and smallest value in a given array.
def big_sum(nums):
      sum= max(nums)+min(nums)
      return sum
<s>[INST]<<SYS>>Given a task and its code, generate test cases for the code.<</SYS>>Write a python function to find the sum of the largest and smallest value in a given array.
def big_sum(nums):
      sum= max(nums)+min(nums)
      return sum[/INST]assert big_sum([1,2,3]) == 4
assert big_sum([-1,2,3,4]) == 3
assert big_sum([2,3,6]) == 8</s>