Fix output in tests (ci)

lib/commandlang_err/src/err.ml

@@ -315,14 +315,14 @@ let handler ?(state = the_state) ?(exn_handler = Fun.const None) f =
 ;;
 
 module For_test = struct
-  let handler ?state ?exn_handler f =
+  let wrap f =
     let init = !am_running_test in
     am_running_test := true;
-    match
-      Fun.protect
-        ~finally:(fun () -> am_running_test := init)
-        (fun () -> handler f ?state ?exn_handler)
-    with
+    Fun.protect ~finally:(fun () -> am_running_test := init) f
+  ;;
+
+  let handler ?state ?exn_handler f =
+    match wrap (fun () -> handler f ?state ?exn_handler) with
     | Ok () -> ()
     | Error code -> Stdlib.prerr_endline (Printf.sprintf "[%d]" code)
   ;;

lib/commandlang_err/src/err.mli

@@ -335,6 +335,12 @@ module For_test : sig
   (** Same as [handler], but won't return the exit code, rather print the code
       at the end in case of a non zero code, like in cram tests. *)
   val handler : ?state:State.t -> ?exn_handler:(exn -> t option) -> (unit -> unit) -> unit
+
+  (** Wrap the execution of a function under an environment proper for test
+      execution. For example, it will turn down the colors in user messages.
+      {!val:handler} already does a [wrap] - this is exposed if you'd like to
+      run some test outside of a handler. *)
+  val wrap : (unit -> 'a) -> 'a
 end
 
 (** {1 Other styles}

lib/commandlang_err/test/test__err.ml

@@ -151,6 +151,8 @@ let%expect_test "state getters" =
 ;;
 
 let%expect_test "multiple errors" =
+  Err.For_test.wrap
+  @@ fun () ->
   Err.error ~loc:(Loc.in_file ~path:(Fpath.v "my/file1")) [ Pp.text "Hello Error1" ];
   Err.error ~loc:(Loc.in_file ~path:(Fpath.v "my/file2")) [ Pp.text "Hello Error1" ];
   [%expect
@@ -165,6 +167,8 @@ let%expect_test "multiple errors" =
 ;;
 
 let%expect_test "error" =
+  Err.For_test.wrap
+  @@ fun () ->
   let state =
     create_state ~config:(Err.Config.create ~mode:Default ~warn_error:false ())
   in