Write a function to find the circumference of a circle.
def circle_circumference(r):
  perimeter=2*3.1415*r
  return perimeter
<s>[INST]<<SYS>>Given a task and its code, generate test cases for the code.<</SYS>>Write a function to find the circumference of a circle.
def circle_circumference(r):
  perimeter=2*3.1415*r
  return perimeter[/INST]assert circle_circumference(10)==62.830000000000005
assert circle_circumference(5)==31.415000000000003
assert circle_circumference(4)==25.132</s>