Adjust tests

test/test_write.ml

@@ -1,15 +1,16 @@
 let to_string () =
   Alcotest.(check string) __LOC__ Fixtures.json_string (Yojson.Safe.to_string Fixtures.json_value)
 
-let to_file () =
+let to_file_tests =
   let test ?newline () =
     let output_file = Filename.temp_file "test_yojson_to_file" ".json" in
     let correction = match newline with
         | None ->
           Yojson.Safe.to_file output_file Fixtures.json_value;
           Fixtures.json_string_newline
         | Some newline -> 
-          Yojson.Safe.to_file ~newline output_file Fixtures.json_value;
+          let suf = match newline with true -> "\n" | false -> "" in
+          Yojson.Safe.to_file ~suf output_file Fixtures.json_value;
           if newline then
             Fixtures.json_string_newline
           else
@@ -25,9 +26,11 @@ let to_file () =
     Alcotest.(check string) __LOC__ correction file_content;
     Sys.remove output_file
   in
-  test ();
-  test ~newline:true ();
-  test ~newline:false ()
+  [
+    "to_file with default settings", `Quick, (fun () -> test ());
+    "to_file with newline", `Quick, (fun () -> test ~newline:true ());
+    "to_file without newline", `Quick, (fun () -> test ~newline:false ());
+  ]
 
 (* List.to_seq is not available on old OCaml versions. *)
 let rec list_to_seq = function
@@ -50,8 +53,8 @@ let seq_to_file () =
        but we don't have a 'testable' instance for JSON values. *)
     Alcotest.fail "seq_{to,from}_file roundtrip failure"
 
-let single_json = [
+let single_json =
+  to_file_tests @ [
   "to_string", `Quick, to_string;
-  "to_file", `Quick, to_file;
   "seq_to_file", `Quick, seq_to_file;
 ]