[minor] Make test_untypeast.ml more readable.

testsuite/tests/compiler-libs/test_untypeast.ml

@@ -8,17 +8,18 @@ let run s =
   let pe = Parse.expression (Lexing.from_string s) in
   let te = Typecore.type_expression Env.initial pe in
   let ute = Untypeast.untype_expression te in
-  Format.asprintf "%a" Pprintast.expression ute
+  Format.printf "%a@." Pprintast.expression ute
 ;;
 
 [%%expect{|
-val run : string -> string = <fun>
+val run : string -> unit = <fun>
 |}];;
 
 run {| match None with Some (Some _) -> () | _ -> () |};;
 
 [%%expect{|
-- : string = "match None with | Some (Some _) -> () | _ -> ()"
+match None with | Some (Some _) -> () | _ -> ()
+- : unit = ()
 |}];;
 
 (***********************************)
@@ -28,12 +29,14 @@ run {| match None with Some (Some _) -> () | _ -> () |};;
 run {| fun x y z -> function w -> x y z w |};;
 
 [%%expect{|
-- : string = "fun x y z -> function | w -> x y z w"
+fun x y z -> function | w -> x y z w
+- : unit = ()
 |}];;
 
 (* 3-ary function returning a 1-ary function *)
 run {| fun x y z -> (function w -> x y z w) |};;
 
 [%%expect{|
-- : string = "fun x y z -> (function | w -> x y z w)"
+fun x y z -> (function | w -> x y z w)
+- : unit = ()
 |}];;