Write a function to find the perimeter of a square.
def square_perimeter(a):
  perimeter=4*a
  return perimeter
<s>[INST]<<SYS>>Given a task and its code, generate test cases for the code.<</SYS>>Write a function to find the perimeter of a square.
def square_perimeter(a):
  perimeter=4*a
  return perimeter[/INST]assert square_perimeter(10)==40
assert square_perimeter(5)==20
assert square_perimeter(4)==16</s>