Test is missing for the function "reorder" of the exercice "Tetragon"

[ghost]

Hi,

I actually test  Introduction te Functionnal Programming (MOOC) . The exercice  Tetragon  asks to write a function reorder . The verification test is incomplete, because all values that this incorrect function returns are considered as correct in the report :

let reorder (p1, p2, p3, p4) = 
  let l = List.sort (fun p p' -> compare (fst p) (fst p')) [p1; p2; p3; p4] in
  let llp = List.nth l 0 in
  let lup = List.nth l 1 in
  let rup = List.nth l 2 in
  let rlp = List.nth l 3 in
  (lup, rup, llp, rlp);;

If you test this function with a well formed tetragon, the points become disordered :

reorder  ((-4,3), (4,4), (-3,-2), (3,-4));;
- : (int * int) * (int * int) * (int * int) * (int * int) = ((-3, -2), (3, -4), (-4, 3), (4, 4))

Maybe teatchers of this exercice should add this test ?