diff --git a/lib/back/cprint1.ml b/lib/back/cprint1.ml
index 01b6c37..d87ee27 100644
--- a/lib/back/cprint1.ml
+++ b/lib/back/cprint1.ml
@@ -6,7 +6,7 @@ let version = "Cprint 4.0 Hugues Cassé et al."
 (*
 ** FrontC Pretty printer
 *)
-let out = ref stdout
+let out = ref (Buffer.create 50)
 let width = ref 80
 let tab = ref 8
 let max_indent = ref 60
@@ -19,6 +19,11 @@ let spaces = ref 0
 let follow = ref 0
 let roll = ref 0
 
+(* override output_string in stdlib *)
+let output_string = Buffer.add_string
+let output_char = Buffer.add_char
+
+
 let print_tab size =
   output_string !out (String.make (size / 8) '\t');
   output_string !out (String.make (size mod 8) ' ')
@@ -755,12 +760,6 @@ and print_def def =
     force_new_line ()
 
 
-(*  print abstrac_syntax -> ()
- **		Pretty printing the given abstract syntax program.
-*)
-let print (result : out_channel) (defs : file) =
-  out := result;
-  print_defs defs
 
 let set_tab t = tab := t
 let set_width w = width := w
diff --git a/lib/test/back_test.ml b/lib/test/back_test.ml
new file mode 100644
index 0000000..0d18801
--- /dev/null
+++ b/lib/test/back_test.ml
@@ -0,0 +1,13 @@
+open Cabs
+module P = Back.Cprint1
+
+let%expect_test "Test: Backend" =
+  let bin =
+    BINARY (ADD, CONSTANT (CONST_INT "1"), CONSTANT (CONST_INT "2"))
+  in
+  P.out := Buffer.create 50;
+  P.print_expression bin 0;
+  P.commit ();
+  P.flush ();
+  !P.out |> Buffer.contents |> print_string;
+  [%expect {| 1 + 2 |}]
diff --git a/lib/test/dune b/lib/test/dune
index 8e3c9a9..0238c37 100644
--- a/lib/test/dune
+++ b/lib/test/dune
@@ -1,6 +1,6 @@
 (library
  (name test)
- (libraries sexplib syntax)
+ (libraries sexplib syntax back)
  (inline_tests)
  (wrapped false)
  (preprocess