hello everyone, having this code snippet, 
```
open OUnit2
open Sum

let make_test test_case_name test_number test_input = 
  test_case_name >:: (fun _ -> assert_equal test_number (sum test_input) ~printer: string_of_int);

let tests = "test suite for sum" >::: [
  make_test "empty" 0 [];
  make_test "one" 1 [1];
  make_test "onetwo" 3 [1; 2];
]

let () = run_test_tt_main tests
```

am getting this sort of error

```
simon@simon-HP-EliteBook-8470p:~/Ocaml$ ocamlbuild -use-ocamlfind -tag debug basics/sum_test.byte
+ ocamlfind ocamldep -package ounit2 -modules basics/sum_test.ml > basics/sum_test.ml.depends
File "basics/sum_test.ml", line 13, characters 0-3:
13 | let () = run_test_tt_main tests
     ^^^
Error: Syntax error
Command exited with code 2.
Compilation unsuccessful after building 1 target (0 cached) in 00:00:00.
simon@simon-HP-EliteBook-8470p:~/Ocaml$ 
```