add expect tests

src/day3.ml

@@ -10,7 +10,8 @@ let priority char =
   | _ -> failwith @@ Printf.sprintf "'%c' is not a valid item" char
 ;;
 
-let part1 lines =
+let part1 () =
+  let lines = Utils.lines_of_input 3 in
   List.fold_left
     (fun acc line ->
       let half_len = String.length line / 2 in
@@ -30,7 +31,8 @@ let part1 lines =
    shout out https://doc.sherlocode.com/ for helping me find Containers and its
    List.chunks and List.reduce functions
 *)
-let part2 lines =
+let part2 () =
+  let lines = Utils.lines_of_input 3 in
   let groups = List.chunks 3 (List.map set_of_string lines) in
   List.fold_left
     (fun acc group ->
@@ -44,9 +46,12 @@ let part2 lines =
     groups
 ;;
 
-let print () =
-  let lines = Utils.lines_of_input 3 in
-  Printf.(
-    printf "Day 3.1: %d\n" @@ part1 lines;
-    printf "Day 3.2: %d\n" @@ part2 lines)
+let%expect_test "Day 3.1" =
+  Printf.printf "%d" @@ part1 ();
+  [%expect {| 7446 |}]
+;;
+
+let%expect_test "Day 3.2" =
+  Printf.printf "%d" @@ part2 ();
+  [%expect {| 2646 |}]
 ;;