diff --git a/.gitignore b/.gitignore
index 58133b97b..6eabfca84 100644
--- a/.gitignore
+++ b/.gitignore
@@ -26,6 +26,7 @@
 /test/test-state
 /test/test-context
 /test/test-basic
+/test/test-data-encoding
 /test/LOG
 
 *~
diff --git a/test/.merlin b/test/.merlin
index 2c4a878ce..b59cb5c6a 100644
--- a/test/.merlin
+++ b/test/.merlin
@@ -17,6 +17,8 @@ S ../src/client
 B ../src/client
 S ../src/client/embedded
 B ../src/client/embedded
+S ./lib
+B ./lib
 FLG -w -40
 PKG lwt
 PKG sodium
diff --git a/test/Makefile b/test/Makefile
index e2dfecc9a..edbdefc00 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -1,5 +1,5 @@
 
-TESTS := store context state basic basic.sh
+TESTS :=  data-encoding store context state basic basic.sh
 
 all: test
 
@@ -62,7 +62,7 @@ ${NODELIB} ${CLIENTLIB}:
 .PHONY: build-test run-test test
 build-test: ${addprefix build-test-,${TESTS}}
 run-test:
-	@$(patsubst %,${MAKE} run-test-% &&, ${TESTS}) \
+	@$(patsubst %,${MAKE} run-test-% ; , ${TESTS}) \
 	  echo && echo "Success" && echo
 test:
 	@${MAKE} --no-print-directory build-test
@@ -168,6 +168,27 @@ test-basic: ${NODELIB} ${CLIENTLIB} ${TEST_BASIC_IMPLS:.ml=.cmx}
 clean::
 	rm -f test-basic
 
+############################################################################
+## data encoding test program
+
+.PHONY:build-test-data-encoding run-test-data-encoding
+build-test-data-encoding: test-data-encoding
+run-test-data-encoding:
+	./test-data-encoding
+
+TEST_DATA_ENCODING_INTFS =
+
+TEST_DATA_ENCODING_IMPLS = \
+  lib/assert.ml \
+  lib/test.ml \
+  test_data_encoding.ml
+
+${TEST_DATA_ENCODING_IMPLS:.ml=.cmx}: ${NODELIB}
+test-data-encoding: ${NODELIB} ${TEST_DATA_ENCODING_IMPLS:.ml=.cmx}
+	ocamlfind ocamlopt -linkall -linkpkg ${OCAMLFLAGS} -o $@ $^
+
+clean::
+	rm -f test-data-encoding
 
 ############################################################################
 ## Generic rules
diff --git a/test/lib/assert.ml b/test/lib/assert.ml
index ceadfbfe6..14aa3fbd7 100644
--- a/test/lib/assert.ml
+++ b/test/lib/assert.ml
@@ -11,12 +11,6 @@ open Kaputt.Abbreviations
 
 include Kaputt.Assertion
 
-let fail_msg fmt =
-  Format.kasprintf Assert.fail_msg fmt
-
-let fail expected given fmt =
-  Format.kasprintf (Assert.fail expected given) fmt
-
 let format_msg = function None -> None | Some msg -> Some (msg ^ "\n")
 
 let equal_persist_list ?msg l1 l2 =
@@ -80,3 +74,25 @@ let equal_result ?msg r1 r2 ~equal_ok ~equal_err =
   | Error e1, Error e2 -> equal_err ?msg e1 e2
   | Ok r, Error e | Error e, Ok r ->
       Assert.fail_msg "Results are not the same"
+
+let equal_exn ?msg exn1 exn2 =
+  let msg = format_msg msg in
+  let prn = Printexc.to_string in
+  Assert.equal ?msg ~prn exn1 exn2
+
+let test_fail ?(msg  = "") ?(prn = Assert.default_printer) f may_fail =
+  try
+    let value = f () in
+    fail "any exception" ("no exception: " ^ prn value) msg
+  with exn ->
+    if not (may_fail exn) then
+      fail "exception"
+        (Printf.sprintf "unexpectec exception: %s" (Printexc.to_string exn))
+        msg
+
+let fail_msg fmt =
+  Format.kasprintf Assert.fail_msg fmt
+
+let fail expected given fmt =
+  Format.kasprintf (Assert.fail expected given) fmt
+
diff --git a/test/lib/assert.mli b/test/lib/assert.mli
index b5010dfd4..08dbdff69 100644
--- a/test/lib/assert.mli
+++ b/test/lib/assert.mli
@@ -42,3 +42,12 @@ val equal_result :
   ('a, 'b) result ->
   equal_ok:(?msg:string -> 'a -> 'a -> 'c) ->
   equal_err:(?msg:string -> 'b -> 'b -> 'c) -> 'c
+
+val equal_exn : ?msg:string -> exn -> exn -> unit
+
+val test_fail :
+  ?msg:string ->
+  ?prn:('a -> string) ->
+  (unit -> 'a) ->
+  (exn -> bool) ->
+  unit
diff --git a/test/lib/test.ml b/test/lib/test.ml
index ba2fc3ea4..35f047b31 100644
--- a/test/lib/test.ml
+++ b/test/lib/test.ml
@@ -11,6 +11,9 @@ open Kaputt.Abbreviations
 
 let keep_dir = try ignore (Sys.getenv "KEEPDIR") ; true with _ -> false
 
+let make_test ~title test =
+  Test.add_simple_test ~title (fun () -> Lwt_main.run (test ()))
+
 let rec remove_dir dir =
   Array.iter (fun file ->
       let f = Filename.concat dir file in
diff --git a/test/test_data_encoding.ml b/test/test_data_encoding.ml
new file mode 100644
index 000000000..ea935debc
--- /dev/null
+++ b/test/test_data_encoding.ml
@@ -0,0 +1,306 @@
+open Data_encoding
+open Context
+open Hash
+
+let (>>=) = Lwt.bind
+let (>|=) = Lwt.(>|=)
+let (//) = Filename.concat
+
+let write_file dir ~name content =
+  let file = (dir // name) in
+  let oc = open_out file in
+  output_string oc content ;
+  close_out oc ;
+  file
+
+let is_invalid_arg = function
+  | Invalid_argument _ -> true
+  | _ -> false
+
+let test_simple_json ?msg ?eq:(equal=Assert.equal) encoding value =
+    let json = Json.construct encoding value in
+    let result = Json.destruct encoding json in
+    equal ?msg value result
+
+let test_simple_bin ?msg ?(equal=Assert.equal) encoding value =
+  let bin = Binary.to_bytes encoding value in
+  let opt = Binary.of_bytes encoding bin in
+  Assert.is_some ?msg opt;
+  let result = match opt with None -> assert false | Some v -> v in
+  equal ?msg value result
+
+let test_json_exn ?msg ?(equal=Assert.equal) encoding value fail =
+  let get_result () =
+    let bin = Json.construct encoding value in
+    Json.destruct encoding bin in
+  Assert.test_fail ?msg get_result fail
+
+let test_bin_exn ?msg ?(equal=Assert.equal) encoding value fail =
+  let get_result () =
+    let bin = Binary.to_bytes encoding value in
+    Binary.of_bytes encoding bin in
+  Assert.test_fail ?msg get_result fail
+
+let test_simple ~msg enc value =
+  test_simple_json ~msg:(msg ^ ": json") enc value ;
+  test_simple_bin ~msg:(msg ^ ": binary") enc value
+
+let test_simple_int ~msg ?(boundary=true) encoding i =
+  let pow y = int_of_float @@ (2. ** float_of_int y) in
+  let i = i - 1 in
+  let range_min = - pow i in
+  let range_max = pow i - 1 in
+  let out_max = pow i in
+  let out_min = - pow i - 1 in
+  test_simple ~msg encoding range_min ;
+  test_simple ~msg encoding range_max ;
+  if boundary then begin
+    test_simple_bin ~msg ~equal:(Assert.not_equal) encoding out_max ;
+    test_simple_bin ~msg ~equal:(Assert.not_equal) encoding out_min
+  end
+
+
+let test_simple_values _ =
+  test_simple ~msg:__LOC__ null ();
+  test_simple ~msg:__LOC__ empty ();
+  test_simple ~msg:__LOC__ (constant "toto") ();
+  test_simple_int ~msg:__LOC__ int8 8;
+  test_simple_int ~msg:__LOC__ int16 16;
+  test_simple_int ~msg:__LOC__ ~boundary:false int31 31;
+  test_simple ~msg:__LOC__ int32 Int32.min_int;
+  test_simple ~msg:__LOC__ int32 Int32.max_int;
+  test_simple ~msg:__LOC__ int64 Int64.min_int;
+  test_simple ~msg:__LOC__ int64 Int64.max_int;
+  test_simple ~msg:__LOC__ bool true;
+  test_simple ~msg:__LOC__ bool false;
+  test_simple ~msg:__LOC__ string "tutu";
+  test_simple ~msg:__LOC__ bytes (MBytes.of_string "titi");
+  test_simple ~msg:__LOC__ float 42.;
+  test_simple ~msg:__LOC__ (option string) (Some "thing");
+  test_simple ~msg:__LOC__ (option string) None;
+  let enum_enc =
+    ["one", 1; "two", 2; "three", 3; "four", 4; "five", 6; "six", 6] in
+  test_simple_bin ~msg:__LOC__ (string_enum enum_enc) 4;
+  test_json_exn ~msg:__LOC__ (string_enum enum_enc) 7 is_invalid_arg ;
+  test_bin_exn ~msg:__LOC__ (string_enum enum_enc) 7
+    (function
+      | No_case_matched -> true
+      | _ -> false) ;
+  (* Should fail *)
+  (* test_bin_exn ~msg:__LOC__ (string_enum ["a", 1; "a", 2]) 2 (...duplicatate...); *)
+  (* test_json_exn ~msg:__LOC__ (string_enum ["a", 1; "a", 2]) 1 (... duplicate...); *)
+
+  Lwt.return_unit
+
+let test_json testdir =
+  let file = testdir // "testing_data_encoding.tezos" in
+  let v = `Float 42. in
+  let f_str = Json.to_string v in
+  Assert.equal_string  ~msg:__LOC__ f_str "[\n  42\n]";
+  Json.read_file (testdir // "NONEXISTINGFILE") >>= fun rf ->
+  Assert.is_none ~msg:__LOC__ rf;
+  Json.write_file file v >>= fun success ->
+  Assert.is_true ~msg:__LOC__ success;
+  Json.read_file file >>= fun opt ->
+  Assert.is_some ~msg:__LOC__ opt;
+  Lwt.return ()
+
+type t = A of int | B of string | C of int | D of string | E
+
+let prn_t = function
+  | A i -> Printf.sprintf "A %d" i
+  | B s -> Printf.sprintf "B %s" s
+  | C i -> Printf.sprintf "C %d" i
+  | D s -> Printf.sprintf "D %s" s
+  | E -> "E"
+
+let test_tag_errors _ =
+    let duplicate_tag () =
+      union [
+        case ~tag:1
+          int8
+          (fun i -> i)
+          (fun i -> Some i) ;
+        case ~tag:1
+          int8
+          (fun i -> i)
+          (fun i -> Some i)] in
+    Assert.test_fail ~msg:__LOC__ duplicate_tag
+      (function Duplicated_tag _ -> true
+              | _ -> false) ;
+    let invalid_tag () =
+      union [
+        case ~tag:(2 lsl 7)
+          int8
+          (fun i -> i)
+          (fun i -> Some i)] in
+    Assert.test_fail ~msg:__LOC__  invalid_tag
+      (function (Invalid_tag (_, `Int8)) -> true
+              | _ -> false) ;
+    Lwt.return_unit
+
+let test_union _ =
+  let enc =
+    (union [
+        case ~tag:1
+          int8
+          (function A i -> Some i | _ -> None)
+          (fun i -> A i) ;
+        case ~tag:2
+          string
+          (function B s -> Some s | _ -> None)
+          (fun s -> B s) ;
+        case ~tag:3
+          int8
+          (function C i -> Some i | _ -> None)
+          (fun i -> C i) ;
+        case ~tag:4
+          (obj2
+             (req "kind" (constant "D"))
+             (req "data" (string)))
+          (function D s -> Some ((), s) | _ -> None)
+          (fun ((), s) -> D s) ;
+      ]) in
+  let jsonA = Json.construct enc (A 1) in
+  let jsonB = Json.construct enc (B "2") in
+  let jsonC = Json.construct enc (C 3) in
+  let jsonD = Json.construct enc (D"4") in
+  Assert.test_fail
+    ~msg:__LOC__ (fun () -> Json.construct enc E) is_invalid_arg ;
+  Assert.equal ~prn:prn_t ~msg:__LOC__ (A 1) (Json.destruct enc jsonA) ;
+  Assert.equal ~prn:prn_t ~msg:__LOC__ (B "2") (Json.destruct enc jsonB) ;
+  Assert.equal ~prn:prn_t ~msg:__LOC__ (A 3) (Json.destruct enc jsonC) ;
+  Assert.equal ~prn:prn_t ~msg:__LOC__ (D "4") (Json.destruct enc jsonD) ;
+  let binA = Binary.to_bytes enc (A 1) in
+  let binB = Binary.to_bytes enc (B "2") in
+  let binC = Binary.to_bytes enc (C 3) in
+  let binD = Binary.to_bytes enc (D "4") in
+  Assert.test_fail ~msg:__LOC__ (fun () -> Binary.to_bytes enc E)
+    (function
+      | No_case_matched -> true
+      | _ -> false) ;
+  let get_result ~msg bin =
+    match Binary.of_bytes enc bin with
+    | None -> Assert.fail_msg "%s" msg
+    | Some bin -> bin in
+  Assert.equal ~prn:prn_t ~msg:__LOC__ (A 1) (get_result ~msg:__LOC__ binA) ;
+  Assert.equal ~prn:prn_t ~msg:__LOC__ (B "2") (get_result ~msg:__LOC__ binB) ;
+  Assert.equal ~prn:prn_t ~msg:__LOC__ (C 3) (get_result ~msg:__LOC__ binC) ;
+  Assert.equal ~prn:prn_t ~msg:__LOC__ (D "4") (get_result ~msg:__LOC__ binD) ;
+  Lwt.return_unit
+
+
+type s = { field : int }
+
+let test_splitted _ =
+  let s_enc =
+    def "s" @@
+    describe
+      ~title:"testsuite encoding test"
+      ~description: "A human readable description" @@
+    conv
+      (fun s -> string_of_int s.field)
+      (fun s -> { field = int_of_string s })
+      string in
+  let enc =
+    (splitted
+       ~binary:string
+       ~json:
+         (union [
+             case ~tag:1
+               string
+               (fun _ -> None)
+               (fun s -> s) ;
+             case ~tag:2
+               s_enc
+               (fun s -> Some { field = int_of_string s })
+              (fun s -> string_of_int s.field) ;
+           ])) in
+  let get_result ~msg bin =
+    match Binary.of_bytes enc bin with
+    | None -> Assert.fail_msg "%s: Cannot parse." msg
+    | Some bin -> bin in
+  let jsonA = Json.construct enc "41" in
+  let jsonB = Json.construct s_enc {field = 42} in
+  let binA = Binary.to_bytes enc "43" in
+  let binB = Binary.to_bytes s_enc {field = 44} in
+  Assert.equal ~msg:__LOC__ "41" (Json.destruct enc jsonA);
+  Assert.equal ~msg:__LOC__ "42" (Json.destruct enc jsonB);
+  Assert.equal ~msg:__LOC__ "43" (get_result ~msg:__LOC__ binA);
+  Assert.equal ~msg:__LOC__ "44" (get_result ~msg:__LOC__ binB);
+  Lwt.return_unit
+
+let test_json_input testdir =
+  let enc =
+    obj1
+      (req "menu" (
+          obj3
+            (req "id" string)
+            (req "value" string)
+            (opt "popup" (
+                obj2
+                  (req "width" int64)
+                  (req "height" int64))))) in
+  begin
+    let file =
+      write_file testdir ~name:"good.json" {|
+ {
+    "menu": {
+        "id": "file",
+        "value": "File",
+        "popup": {
+            "width" : 42,
+            "height" : 52
+        }
+    }
+}
+|}
+    in
+    Json.read_file file >>= function
+      None -> Assert.fail_msg "Cannot parse \"good.json\"."
+    | Some json ->
+        let (id, value, popup) = Json.destruct enc json in
+        Assert.equal_string ~msg:__LOC__ "file" id;
+        Assert.equal_string ~msg:__LOC__ "File" value;
+        Assert.is_some ~msg:__LOC__ popup;
+        let w,h = match popup with None -> assert false | Some (w,h) -> w,h in
+        Assert.equal_int64 ~msg:__LOC__ 42L w;
+        Assert.equal_int64 ~msg:__LOC__ 52L h;
+        Lwt.return_unit
+  end >>= fun () ->
+  let enc =
+    obj2
+      (req "kind" (string))
+      (req "data" (int64)) in
+  begin
+    let file =
+      write_file testdir ~name:"unknown.json" {|
+{
+  "kind" : "int64",
+  "data" : "42",
+  "unknown" : 2
+}
+|}
+    in
+    Json.read_file file >>= function
+      None -> Assert.fail_msg "Cannot parse \"unknown.json\"."
+    | Some json ->
+        Assert.test_fail ~msg:__LOC__
+          (fun () -> ignore (Json.destruct enc json))
+          (function
+            | Json.Unexpected_field "unknown" -> true
+            | _ -> false) ;
+        Lwt.return_unit
+  end
+
+let tests = [
+  "simple", test_simple_values ;
+  "json", test_json ;
+  "union", test_union ;
+  "splitted", test_splitted ;
+  "json.input", test_json_input ;
+  "tags", test_tag_errors ;
+]
+
+let () =
+  Test.run "data_encoding." tests