diff --git a/c/.gitignore b/c/.gitignore
deleted file mode 100644
index dba0160..0000000
--- a/c/.gitignore
+++ /dev/null
@@ -1,3 +0,0 @@
-/testocamlrandom
-/testxoshiro
-/testsplitmix
diff --git a/c/Makefile b/c/Makefile
deleted file mode 100644
index 691c63f..0000000
--- a/c/Makefile
+++ /dev/null
@@ -1,15 +0,0 @@
-all: testxoshiro testocamlrandom testsplitmix
-
-testsplitmix: testsplitmix.c splitmix64.c splitmix64.h
-	cc -o $@ $< splitmix64.c
-
-testxoshiro: testxoshiro.c xoshiro256pp.c xoshiro256pp.h
-	cc -o $@ $< xoshiro256pp.c
-
-testocamlrandom: testocamlrandom.c ocamlrandom.c ocamlrandom.h
-	cc -o $@ $< ocamlrandom.c
-
-clean:
-	rm -f testxoshiro testocamlrandom testsplitmix
-
-.PHONY: all clean
diff --git a/c/ocamlrandom.c b/c/ocamlrandom.c
deleted file mode 100644
index 6c90d48..0000000
--- a/c/ocamlrandom.c
+++ /dev/null
@@ -1,24 +0,0 @@
-static int s[55] = {
-  0x3ae2522b, 0x1d8d4634, 0x15b4fad0, 0x18b14ace, 0x12f8a3c4, 0x3b086c47,
-  0x16d467d6, 0x101d91c7, 0x321df177, 0x0176c193, 0x1ff72bf1, 0x1e889109,
-  0x0b464b18, 0x2b86b97c, 0x0891da48, 0x03137463, 0x085ac5a1, 0x15d61f2f,
-  0x3bced359, 0x29c1c132, 0x3a86766e, 0x366d8c86, 0x1f5b6222, 0x3ce1b59f,
-  0x2ebf78e1, 0x27cd1b86, 0x258f3dc3, 0x389a8194, 0x02e4c44c, 0x18c43f7d,
-  0x0f6e534f, 0x1e7df359, 0x055d0b7e, 0x10e84e7e, 0x126198e4, 0x0e7722cb,
-  0x1cbede28, 0x3391b964, 0x3d40e92a, 0x0c59933d, 0x0b8cd0b7, 0x24efff1c,
-  0x2803fdaa, 0x08ebc72e, 0x0f522e32, 0x05398edc, 0x2144a04c, 0x0aef3cbd,
-  0x01ad4719, 0x35b93cd6, 0x2a559d4f, 0x1e6fd768, 0x26e27f36, 0x186f18c3,
-  0x2fbf967a,
-};
-
-static int idx = 0;
-
-int bits() {
-  idx = (idx + 1) % 55;
-  int curval = s[idx];
-  int newval = s[(idx + 24) % 55] + (curval ^ ((curval >> 25) & 0x1F));
-  int newval30 = newval & 0x3FFFFFFF;
-  s[idx] = newval30;
-  return newval30;
-}
-
diff --git a/c/ocamlrandom.h b/c/ocamlrandom.h
deleted file mode 100644
index 6ca5c74..0000000
--- a/c/ocamlrandom.h
+++ /dev/null
@@ -1 +0,0 @@
-int bits();
diff --git a/c/splitmix64.h b/c/splitmix64.h
deleted file mode 100644
index 9b48294..0000000
--- a/c/splitmix64.h
+++ /dev/null
@@ -1,3 +0,0 @@
-#include <stdint.h>
-
-uint64_t next();
diff --git a/c/testocamlrandom.c b/c/testocamlrandom.c
deleted file mode 100644
index 77bce0c..0000000
--- a/c/testocamlrandom.c
+++ /dev/null
@@ -1,14 +0,0 @@
-#include <stdlib.h>
-#include <stdio.h>
-#include "ocamlrandom.h"
-
-int main(int argc, char* argv[]) {
-  int n = 10;
-  if (argc == 2) n = atoi(argv[1]);
-
-  for (int i = 0; i < n; i++)
-    printf("%08x\n", bits());
-
-  return 0;
-}
-
diff --git a/c/testsplitmix.c b/c/testsplitmix.c
deleted file mode 100644
index 2aa6e34..0000000
--- a/c/testsplitmix.c
+++ /dev/null
@@ -1,16 +0,0 @@
-#include <stdint.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include "splitmix64.h"
-
-
-int main(int argc, char* argv[]) {
-  int n = 10;
-  if (argc == 2) n = atoi(argv[1]);
-
-  for (int i = 0; i < n; i++)
-    printf("%016lx\n", next());
-
-  return 0;
-}
-
diff --git a/c/testxoshiro.c b/c/testxoshiro.c
deleted file mode 100644
index 39bdb2d..0000000
--- a/c/testxoshiro.c
+++ /dev/null
@@ -1,15 +0,0 @@
-#include <assert.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <stdint.h>
-#include "xoshiro256pp.h"
-
-int main(int argc, const char* argv[]) {
-  int n = 10;
-  if (argc == 2) n = atoi(argv[1]);
-
-  for (int i = 0; i < n; i++)
-    printf("%016lx\n", next());
-
-  return 0;
-}
diff --git a/compare.sh b/compare.sh
deleted file mode 100755
index 4904341..0000000
--- a/compare.sh
+++ /dev/null
@@ -1,17 +0,0 @@
-#!/bin/sh
-
-set -e
-
-compare () {
-  echo "Comparing '$1' and '$2'..."
-  tmp="$(mktemp)"
-  "$1" 1000 > "$tmp"
-  test -z "$("$2" 1000 | diff "$tmp" -)"
-  rm -f "$tmp"
-}
-
-make -C ocaml tests
-make -C c all
-
-compare ocaml/_build/default/tests/splitmix.exe c/testsplitmix
-echo OK!
diff --git a/dune b/dune
new file mode 100644
index 0000000..75bd9a5
--- /dev/null
+++ b/dune
@@ -0,0 +1,2 @@
+(env
+ (_ (c_flags :standard -Werror -Wall -Wextra -pedantic)))
diff --git a/ocaml/dune-project b/dune-project
similarity index 100%
rename from ocaml/dune-project
rename to dune-project
diff --git a/ocaml/Makefile b/ocaml/Makefile
deleted file mode 100644
index 1c48a5c..0000000
--- a/ocaml/Makefile
+++ /dev/null
@@ -1,14 +0,0 @@
-all: tests bench
-
-tests:
-	dune build ./tests/ocamlrandom.exe
-	dune build ./tests/xoshiro.exe
-	dune build ./tests/splitmix.exe
-
-bench:
-	dune build ./bench.exe
-
-clean:
-	dune clean
-
-.PHONY: all clean bench tests
diff --git a/ocaml/bench.ml b/ocaml/bench.ml
deleted file mode 100644
index 1ed8f82..0000000
--- a/ocaml/bench.ml
+++ /dev/null
@@ -1,57 +0,0 @@
-open Xoshiro
-module B = Core_bench.Bench
-module Command = Core.Command
-
-module Random_Stdlib       = MakeRandom.Basic(Random)
-module Random_X256pp_Int   = MakeRandom.Basic(X256pp.Int)
-module Random_X256pp_Int64 = MakeRandom.Basic(X256pp.Int64)
-module Random_X256pp_C     = MakeRandom.Basic(X256pp.C)
-
-let bits () =
-  Command.run @@ B.make_command [
-    B.Test.create ~name:"Random.bits" (fun () ->
-        Random.bits ());
-    B.Test.create ~name:"X256pp.Int.bits" (fun () ->
-        X256pp.Int.bits ());
-    B.Test.create ~name:"X256pp.Int64.bits" (fun () ->
-        X256pp.Int64.bits ());
-    B.Test.create ~name:"X256pp.Int64.bits62" (fun () ->
-        X256pp.Int64.bits62 ());
-    B.Test.create ~name:"X256pp.C.bits" (fun () ->
-        X256pp.C.bits ());
-    B.Test.create ~name:"X256pp.C.bits62" (fun () ->
-        X256pp.C.bits62 ());
-  ]
-
-let float () =
-  Command.run @@ B.make_command [
-    B.Test.create ~name:"Random.float" (fun () ->
-        Random.float 1.);
-    B.Test.create ~name:"X256pp.Int64.float" (fun () ->
-        X256pp.Int64.float 1.);
-    B.Test.create ~name:"X256pp.C.float" (fun () ->
-        X256pp.C.float 1.);
-    B.Test.create ~name:"MakeRandom(X256pp.Int).float" (fun () ->
-        Random_X256pp_Int.float 1.);
-    B.Test.create ~name:"MakeRandom(X256pp.Int64).float" (fun () ->
-        Random_X256pp_Int64.float 1.);
-    B.Test.create ~name:"MakeRandom(X256pp.C).float" (fun () ->
-        Random_X256pp_C.float 1.);
-  ]
-
-let int64 () =
-  Command.run @@ B.make_command [
-    B.Test.create ~name:"MakeRandom(Random).int64" (fun () ->
-        Random_Stdlib.int64 Int64.max_int);
-    B.Test.create ~name:"MakeRandom(X256pp.Int).int64" (fun () ->
-        Random_X256pp_Int.int64 Int64.max_int);
-    B.Test.create ~name:"MakeRandom(X256pp.Int64).int64" (fun () ->
-        Random_X256pp_Int64.int64 Int64.max_int);
-    B.Test.create ~name:"MakeRandom(X256pp.C).int64" (fun () ->
-        Random_X256pp_C.int64 Int64.max_int);
-  ]
-
-let () =
-  bits ();
-  float ();
-  int64 ()
diff --git a/ocaml/dune b/ocaml/dune
deleted file mode 100644
index 094d9f8..0000000
--- a/ocaml/dune
+++ /dev/null
@@ -1,4 +0,0 @@
-(executable
- (name bench)
- (libraries xoshiro makeRandom core_bench)
- (modules Bench))
diff --git a/ocaml/tests/dune b/ocaml/tests/dune
deleted file mode 100644
index 5189e02..0000000
--- a/ocaml/tests/dune
+++ /dev/null
@@ -1,13 +0,0 @@
-(executable
- (name xoshiro)
- (modules xoshiro)
- (libraries xoshiro))
-
-(executable
- (name ocamlrandom)
- (modules ocamlrandom))
-
-(executable
- (name splitmix)
- (modules splitmix)
- (libraries splitmix))
diff --git a/ocaml/tests/ocamlrandom.ml b/ocaml/tests/ocamlrandom.ml
deleted file mode 100644
index 00344a3..0000000
--- a/ocaml/tests/ocamlrandom.ml
+++ /dev/null
@@ -1,10 +0,0 @@
-let () =
-  let n =
-    if Array.length Sys.argv = 2
-    then int_of_string Sys.argv.(1)
-    else 10
-  in
-
-  for _ = 1 to n do
-    Format.printf "%08x\n" (Random.bits ())
-  done
diff --git a/ocaml/tests/splitmix.ml b/ocaml/tests/splitmix.ml
deleted file mode 100644
index eb3e35a..0000000
--- a/ocaml/tests/splitmix.ml
+++ /dev/null
@@ -1,13 +0,0 @@
-open Splitmix
-
-let () =
-  let n =
-    if Array.length Sys.argv = 2
-    then int_of_string Sys.argv.(1)
-    else 10
-  in
-
-  let state = ref 0xdead42beef37ca7aL in
-  for _ = 1 to n do
-    Format.printf "%016Lx@." (Sm64.next state)
-  done
diff --git a/ocaml/tests/xoshiro.ml b/ocaml/tests/xoshiro.ml
deleted file mode 100644
index e615baa..0000000
--- a/ocaml/tests/xoshiro.ml
+++ /dev/null
@@ -1,15 +0,0 @@
-open Xoshiro
-
-let () =
-  let n =
-    if Array.length Sys.argv = 2
-    then int_of_string Sys.argv.(1)
-    else 10
-  in
-
-  for _ = 1 to n do
-    let hi, lo = X256pp.Int.next () in
-    Format.printf "%08x%08x " hi lo;
-    Format.printf "%016Lx " (X256pp.Int64.next ());
-    Format.printf "%08x@." (X256pp.C.bits ())
-  done
diff --git a/ocaml/xoshiro/dune b/ocaml/xoshiro/dune
deleted file mode 100644
index baefbf5..0000000
--- a/ocaml/xoshiro/dune
+++ /dev/null
@@ -1,5 +0,0 @@
-(include_subdirs unqualified)
-
-(library
- (name xoshiro)
- (foreign_stubs (language c) (names x256pp)))
diff --git a/ocaml/xoshiro/x256pp_c/x256pp.c b/ocaml/xoshiro/x256pp_c/x256pp.c
deleted file mode 100644
index c768a4d..0000000
--- a/ocaml/xoshiro/x256pp_c/x256pp.c
+++ /dev/null
@@ -1,55 +0,0 @@
-#include "x256pp.h"
-#include <stdint.h>
-#include <stdio.h>
-
-static inline uint64_t rotl(const uint64_t x, int k) {
-	return (x << k) | (x >> (64 - k));
-}
-
-static uint64_t s[4] = {
-  0xdeadbeefdeadbeef,
-  0x4242424242424242,
-  0x3737373737373737,
-  0xca7aca7aca7aca7a
-};
-
-static uint64_t next(void) {
-	const uint64_t result = rotl(s[0] + s[3], 23) + s[0];
-
-	const uint64_t t = s[1] << 17;
-
-	s[2] ^= s[0];
-	s[3] ^= s[1];
-	s[1] ^= s[2];
-	s[0] ^= s[3];
-
-	s[2] ^= t;
-
-	s[3] = rotl(s[3], 45);
-
-	return result;
-}
-
-static long int buf = 0;
-static int buf_len = 0;
-static const uint64_t mask30 = (1 << 30) - 1;
-
-CAMLprim value x256pp_bits() {
-  if (buf_len == 0) {
-    buf = next();
-    buf_len = 2;
-  }
-  long int res = buf & mask30;
-  buf_len--;
-  buf = buf >> 32;
-  return Val_long(res);
-}
-
-CAMLprim value x256pp_bits62() {
-  return Val_long(next() >> 2);
-}
-
-CAMLprim value x256pp_double(value f) {
-  double d = (next() >> 11) * 0x1.0p-53 * Double_val(f);
-  return caml_copy_double(d);
-}
diff --git a/ocaml/xoshiro/x256pp_c/x256pp.h b/ocaml/xoshiro/x256pp_c/x256pp.h
deleted file mode 100644
index 77d8b8a..0000000
--- a/ocaml/xoshiro/x256pp_c/x256pp.h
+++ /dev/null
@@ -1,12 +0,0 @@
-#ifndef X256PP_H
-#define X256PP_H 1
-
-#define CAML_NAME_SPACE
-#include <caml/mlvalues.h>
-#include <caml/alloc.h>
-
-CAMLprim value x256pp_bits();
-CAMLprim value x256pp_bits62();
-CAMLprim value x256pp_double(value);
-
-#endif
diff --git a/ocaml/.gitignore b/prng/src/.gitignore
similarity index 100%
rename from ocaml/.gitignore
rename to prng/src/.gitignore
diff --git a/ocaml/make-random/bench.ml b/prng/src/make-random/bench.ml
similarity index 100%
rename from ocaml/make-random/bench.ml
rename to prng/src/make-random/bench.ml
diff --git a/ocaml/make-random/dune b/prng/src/make-random/dune
similarity index 100%
rename from ocaml/make-random/dune
rename to prng/src/make-random/dune
diff --git a/ocaml/make-random/makeRandom.ml b/prng/src/make-random/makeRandom.ml
similarity index 100%
rename from ocaml/make-random/makeRandom.ml
rename to prng/src/make-random/makeRandom.ml
diff --git a/ocaml/make-random/test.ml b/prng/src/make-random/test.ml
similarity index 100%
rename from ocaml/make-random/test.ml
rename to prng/src/make-random/test.ml
diff --git a/ocaml/splitmix/dune b/prng/src/splitmix/dune
similarity index 100%
rename from ocaml/splitmix/dune
rename to prng/src/splitmix/dune
diff --git a/ocaml/splitmix/sm64.ml b/prng/src/splitmix/sm64.ml
similarity index 100%
rename from ocaml/splitmix/sm64.ml
rename to prng/src/splitmix/sm64.ml
diff --git a/prng/src/splitmix/tests/dune b/prng/src/splitmix/tests/dune
new file mode 100644
index 0000000..58d28fa
--- /dev/null
+++ b/prng/src/splitmix/tests/dune
@@ -0,0 +1,13 @@
+(executable
+ (name sm64_ocaml)
+ (libraries splitmix testutils))
+
+(rule
+ (target sm64_c.exe)
+ (deps reference.h (:codedeps sm64_c.c reference.c %{lib-private:testutils:libtestutils.a}))
+ (action
+  (run %{cc} -o %{target} %{codedeps})))
+
+(rule (with-stdout-to sm64_ocaml.output (run ./sm64_ocaml.exe --nb=1000)))
+(rule (with-stdout-to sm64_c.output     (run ./sm64_c.exe     --nb=1000)))
+(rule (alias runtest) (action (diff sm64_ocaml.output sm64_c.output)))
diff --git a/c/splitmix64.c b/prng/src/splitmix/tests/reference.c
similarity index 72%
rename from c/splitmix64.c
rename to prng/src/splitmix/tests/reference.c
index 6dcbad8..b99dbeb 100644
--- a/c/splitmix64.c
+++ b/prng/src/splitmix/tests/reference.c
@@ -9,13 +9,13 @@ See <http://creativecommons.org/publicdomain/zero/1.0/>. */
 #include <stdint.h>
 
 /* This is a fixed-increment version of Java 8's SplittableRandom generator
-   See http://dx.doi.org/10.1145/2714064.2660195 and
+   See http://dx.doi.org/10.1145/2714064.2660195 and 
    http://docs.oracle.com/javase/8/docs/api/java/util/SplittableRandom.html
 
    It is a very fast generator passing BigCrush, and it can be useful if
    for some reason you absolutely want 64 bits of state. */
 
-static uint64_t x = 0xdead42beef37ca7a; /* The state can be seeded with any value. */
+static uint64_t x; /* The state can be seeded with any value. */
 
 uint64_t next() {
 	uint64_t z = (x += 0x9e3779b97f4a7c15);
@@ -24,3 +24,10 @@ uint64_t next() {
 	return z ^ (z >> 31);
 }
 
+// --------------------------------
+// Above this line: verbatim copy of http://prng.di.unimi.it/splitmix64.c
+// Below: added by us for testing purpose
+
+void seed(uint64_t s) {
+  x = s;
+}
diff --git a/prng/src/splitmix/tests/reference.h b/prng/src/splitmix/tests/reference.h
new file mode 100644
index 0000000..536a2b9
--- /dev/null
+++ b/prng/src/splitmix/tests/reference.h
@@ -0,0 +1,9 @@
+#ifndef SPLITMIX64_H
+#define SPLITMIX64_H 1
+
+#include <stdint.h>
+
+uint64_t next();
+void seed(uint64_t);
+
+#endif
diff --git a/prng/src/splitmix/tests/sm64_c.c b/prng/src/splitmix/tests/sm64_c.c
new file mode 100644
index 0000000..24bdbb3
--- /dev/null
+++ b/prng/src/splitmix/tests/sm64_c.c
@@ -0,0 +1,6 @@
+#include "reference.h" // seed, next
+#include "../../testutils/testutils.h" // testutils_run
+
+int main(int argc, char* argv[]) {
+  return testutils_run(argc, argv, seed, next);
+}
diff --git a/prng/src/splitmix/tests/sm64_ocaml.ml b/prng/src/splitmix/tests/sm64_ocaml.ml
new file mode 100644
index 0000000..8cd0e97
--- /dev/null
+++ b/prng/src/splitmix/tests/sm64_ocaml.ml
@@ -0,0 +1,7 @@
+open Splitmix
+
+let () =
+  let state = ref 0L in
+  Testutils.run
+    ~seed_f:(fun s -> state := s)
+    ~next:(fun () -> Sm64.next state)
diff --git a/prng/src/testutils/dune b/prng/src/testutils/dune
new file mode 100644
index 0000000..ef7ee52
--- /dev/null
+++ b/prng/src/testutils/dune
@@ -0,0 +1,7 @@
+(foreign_library
+ (archive_name testutils)
+ (language c)
+ (names testutils))
+
+(library
+ (name testutils))
diff --git a/prng/src/testutils/testutils.c b/prng/src/testutils/testutils.c
new file mode 100644
index 0000000..9b7b233
--- /dev/null
+++ b/prng/src/testutils/testutils.c
@@ -0,0 +1,52 @@
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <getopt.h>
+
+int usage(const char* prog_name) {
+  fprintf(stderr, "%s [--seed=SEED] [--nb=N]\n", prog_name);
+  return 1;
+}
+
+int testutils_run(
+    int argc, char* argv[], void(*seed_func)(uint64_t), uint64_t(*next)(void)
+) {
+  long nb_iterations = -1;
+  uint64_t seed = 0xdd6d0e2e849e51ad;
+
+  struct option long_options[] = {
+    {"seed", optional_argument, NULL, 's'},
+    {"nb", optional_argument, NULL, 'n'},
+  };
+
+  while (1) {
+    int option_index = 0;
+    int c = getopt_long(argc, argv, "", long_options, &option_index);
+    char* endptr;
+    if (c == -1) break;
+    switch (c) {
+      case 's':
+        if (optarg == NULL) return usage(argv[0]);
+        seed = strtoull(optarg, &endptr, 10);
+        if (endptr == optarg || *endptr != '\0') return usage(argv[0]);
+        break;
+      case 'n':
+        if (optarg == NULL) return usage(argv[0]);
+        nb_iterations = strtol(optarg, &endptr, 10);
+        if (endptr == optarg || *endptr != '\0') return usage(argv[0]);
+        break;
+      default:
+        return usage(argv[0]);
+    }
+  }
+
+  if (optind < argc) return usage(argv[0]);
+
+  seed_func(seed);
+  for (long i = 0; i != nb_iterations; i++) {
+    printf("%lx\n", next());
+  }
+
+  return 0;
+}
+
diff --git a/prng/src/testutils/testutils.h b/prng/src/testutils/testutils.h
new file mode 100644
index 0000000..d60fcc4
--- /dev/null
+++ b/prng/src/testutils/testutils.h
@@ -0,0 +1,7 @@
+#ifndef TESTUTILS_H
+#define TESTUTILS_H 1
+
+#include <stdint.h>
+int testutils_run(int, char**, void(*)(uint64_t), uint64_t(*)(void));
+
+#endif
diff --git a/prng/src/testutils/testutils.ml b/prng/src/testutils/testutils.ml
new file mode 100644
index 0000000..1f1dc5f
--- /dev/null
+++ b/prng/src/testutils/testutils.ml
@@ -0,0 +1,28 @@
+let run ~seed_f ~next =
+  let seed = ref 0xdd6d0e2e849e51adL in
+  let nb_iterations = ref (-1) in
+
+  let speclist = [
+    (
+      "--nb",
+      Arg.Set_int nb_iterations,
+      "Number of random integers to generate"
+    );
+    (
+      "--seed",
+      Arg.String (fun n -> seed := Int64.of_string n),
+      "64-bit seed");
+  ] |> Arg.align
+  in
+
+  let usage =
+    Format.sprintf "%s [--seed=SEED] [--nb=N]" Sys.argv.(0)
+  in
+
+  Arg.parse speclist (fun _ -> invalid_arg "run") usage;
+  seed_f !seed;
+  let i = ref 0 in
+  while !i <> !nb_iterations do
+    Format.printf "%Lx@." (next ());
+    incr i
+  done
diff --git a/prng/src/xoshiro/dune b/prng/src/xoshiro/dune
new file mode 100644
index 0000000..fa217cc
--- /dev/null
+++ b/prng/src/xoshiro/dune
@@ -0,0 +1,3 @@
+(library
+ (name xoshiro)
+ (libraries splitmix))
diff --git a/prng/src/xoshiro/tests/dune b/prng/src/xoshiro/tests/dune
new file mode 100644
index 0000000..9794944
--- /dev/null
+++ b/prng/src/xoshiro/tests/dune
@@ -0,0 +1,17 @@
+(executables
+ (names int64 int)
+ (libraries xoshiro testutils splitmix))
+
+(rule
+ (target x256pp_c.exe)
+ (deps reference.h (:codedeps x256pp_c.c reference.c %{lib-private:testutils:libtestutils.a}))
+ (action
+  (run %{cc} -o %{target} %{codedeps})))
+
+
+(rule (with-stdout-to x256pp_int.output   (run ./int.exe      --nb=1000)))
+(rule (with-stdout-to x256pp_int64.output (run ./int64.exe    --nb=1000)))
+(rule (with-stdout-to x256pp_c.output     (run ./x256pp_c.exe --nb=1000)))
+
+(rule (alias runtest) (action (diff x256pp_int.output   x256pp_c.output)))
+(rule (alias runtest) (action (diff x256pp_int64.output x256pp_c.output)))
diff --git a/prng/src/xoshiro/tests/int.ml b/prng/src/xoshiro/tests/int.ml
new file mode 100644
index 0000000..dbe2568
--- /dev/null
+++ b/prng/src/xoshiro/tests/int.ml
@@ -0,0 +1,24 @@
+open Xoshiro
+
+let int_int_to_int64 (hi, lo) =
+  let open Stdlib.Int64 in
+  logxor (shift_left (of_int hi) 32) (of_int lo)
+
+let int64_to_int_int n =
+  let open Stdlib.Int64 in
+  let hi = to_int (shift_right_logical n 32) in
+  let lo = to_int (logand n 0xFFFFFFFFL) in
+  (hi, lo)
+
+let ocaml_seed seed =
+  let s = ref seed in
+  for i = 0 to 3 do
+    let hi, lo = Splitmix.Sm64.next s |> int64_to_int_int in
+    X256pp.Int.state.(2 * i) <- hi;
+    X256pp.Int.state.(2 * i + 1) <- lo
+  done
+
+let () =
+  Testutils.run
+    ~seed_f:ocaml_seed
+    ~next:(fun () -> X256pp.Int.next () |> int_int_to_int64)
diff --git a/prng/src/xoshiro/tests/int64.ml b/prng/src/xoshiro/tests/int64.ml
new file mode 100644
index 0000000..cf247e8
--- /dev/null
+++ b/prng/src/xoshiro/tests/int64.ml
@@ -0,0 +1,10 @@
+open Xoshiro
+
+let () =
+  Testutils.run
+    ~seed_f:(fun seed ->
+      let s = ref seed in
+      for i = 0 to 3 do
+        X256pp.Int64.s.(i) <- Splitmix.Sm64.next s
+      done)
+    ~next:X256pp.Int64.next
diff --git a/c/xoshiro256pp.c b/prng/src/xoshiro/tests/reference.c
similarity index 64%
rename from c/xoshiro256pp.c
rename to prng/src/xoshiro/tests/reference.c
index 30685eb..29d78f8 100644
--- a/c/xoshiro256pp.c
+++ b/prng/src/xoshiro/tests/reference.c
@@ -7,7 +7,6 @@ worldwide. This software is distributed without any warranty.
 See <http://creativecommons.org/publicdomain/zero/1.0/>. */
 
 #include <stdint.h>
-#include <stdio.h>
 
 /* This is xoshiro256++ 1.0, one of our all-purpose, rock-solid generators.
    It has excellent (sub-ns) speed, a state (256 bits) that is large
@@ -25,12 +24,7 @@ static inline uint64_t rotl(const uint64_t x, int k) {
 }
 
 
-static uint64_t s[4] = {
-  0xdeadbeefdeadbeef,
-  0x4242424242424242,
-  0x3737373737373737,
-  0xca7aca7aca7aca7a
-};
+static uint64_t s[4];
 
 uint64_t next(void) {
 	const uint64_t result = rotl(s[0] + s[3], 23) + s[0];
@@ -48,3 +42,23 @@ uint64_t next(void) {
 
 	return result;
 }
+
+// --------------------------------
+// Above this line: verbatim copy of http://prng.di.unimi.it/xoshiro256plusplus.c
+// without the `jump` and `long_jump` functions.
+// Below: added by us for testing purpose
+
+// Use splitmix64 to seed xoshiro as suggested by Vigna.
+uint64_t splitmix64_stateless(uint64_t* state) {
+	uint64_t z = (*state += 0x9e3779b97f4a7c15);
+	z = (z ^ (z >> 30)) * 0xbf58476d1ce4e5b9;
+	z = (z ^ (z >> 27)) * 0x94d049bb133111eb;
+	return z ^ (z >> 31);
+}
+
+void seed(uint64_t x) {
+  uint64_t splitmix_state = x;
+  for (int i = 0; i < 4; i++) {
+    s[i] = splitmix64_stateless(&splitmix_state);
+  }
+}
diff --git a/c/xoshiro256pp.h b/prng/src/xoshiro/tests/reference.h
similarity index 81%
rename from c/xoshiro256pp.h
rename to prng/src/xoshiro/tests/reference.h
index 4f24453..1995ec0 100644
--- a/c/xoshiro256pp.h
+++ b/prng/src/xoshiro/tests/reference.h
@@ -4,5 +4,7 @@
 #include <stdint.h>
 
 uint64_t next();
+void seed(uint64_t);
 
 #endif
+
diff --git a/prng/src/xoshiro/tests/x256pp_c.c b/prng/src/xoshiro/tests/x256pp_c.c
new file mode 100644
index 0000000..24bdbb3
--- /dev/null
+++ b/prng/src/xoshiro/tests/x256pp_c.c
@@ -0,0 +1,6 @@
+#include "reference.h" // seed, next
+#include "../../testutils/testutils.h" // testutils_run
+
+int main(int argc, char* argv[]) {
+  return testutils_run(argc, argv, seed, next);
+}
diff --git a/ocaml/xoshiro/x256pp.ml b/prng/src/xoshiro/x256pp.ml
similarity index 96%
rename from ocaml/xoshiro/x256pp.ml
rename to prng/src/xoshiro/x256pp.ml
index 44a8ed5..23dbaca 100644
--- a/ocaml/xoshiro/x256pp.ml
+++ b/prng/src/xoshiro/x256pp.ml
@@ -162,9 +162,3 @@ module Int64 = struct
   let float x =
     Int64.(to_float (shift_right_logical (next ()) 11)) *. 0x1.0p-53 *. x
 end
-
-module C = struct
-  external bits: unit -> int = "x256pp_bits"
-  external bits62: unit -> int = "x256pp_bits62"
-  external float: float -> float = "x256pp_double"
-end
diff --git a/testu01/testu01/bbattery_stubs.c b/testu01/testu01/bbattery_stubs.c
index acc5ab7..3e6f627 100644
--- a/testu01/testu01/bbattery_stubs.c
+++ b/testu01/testu01/bbattery_stubs.c
@@ -37,7 +37,7 @@ value caml_bbattery_SmallCrush(value bgen) {
 
 value caml_bbattery_SmallCrushFile(value filename) {
   CAMLparam1(filename);
-  bbattery_SmallCrushFile(Bytes_val(filename));
+  bbattery_SmallCrushFile((char*)Bytes_val(filename));
   CAMLreturn(Val_unit);
 }
 
@@ -97,7 +97,7 @@ value caml_bbattery_Rabbit(value bgen, value nb) {
 
 value caml_bbattery_RabbitFile(value filename, value nb) {
   CAMLparam2(filename, nb);
-  bbattery_RabbitFile (Bytes_val(filename), Double_val(nb));
+  bbattery_RabbitFile ((char*)Bytes_val(filename), Double_val(nb));
   CAMLreturn(Val_unit);
 }
 
@@ -121,7 +121,7 @@ value caml_bbattery_Alphabit(value bgen, value nb, value r, value s) {
 
 value caml_bbattery_AlphabitFile(value filename, value nb) {
   CAMLparam2(filename, nb);
-  bbattery_AlphabitFile (Bytes_val(filename), Double_val(nb));
+  bbattery_AlphabitFile ((char*)Bytes_val(filename), Double_val(nb));
   CAMLreturn(Val_unit);
 }
 
@@ -143,7 +143,7 @@ value caml_bbattery_BlockAlphabit(value bgen, value nb, value r, value s) {
 
 value caml_bbattery_BlockAlphabitFile(value filename, value nb) {
   CAMLparam2(filename, nb);
-  bbattery_BlockAlphabitFile (Bytes_val(filename), Double_val(nb));
+  bbattery_BlockAlphabitFile ((char*)Bytes_val(filename), Double_val(nb));
   CAMLreturn(Val_unit);
 }
 
@@ -156,6 +156,7 @@ value caml_bbattery_RepeatBlockAlphabit(value bgen, value nb, value r, value s,
   CAMLreturn(Val_unit);
 }
 value camlbytecode_bbattery_RepeatBlockAlphabit(value * argv, int argn) {
+  IGNORE(argn);
   return caml_bbattery_RepeatBlockAlphabit(argv[0], argv[1], argv[2], argv[3], argv[4], argv[5]);
 }
 
@@ -179,6 +180,6 @@ value caml_bbattery_FIPS_140_2(value bgen) {
 
 value caml_bbattery_FIPS_140_2File(value filename) {
   CAMLparam1(filename);
-  bbattery_FIPS_140_2File(Bytes_val(filename));
+  bbattery_FIPS_140_2File((char*)Bytes_val(filename));
   CAMLreturn(Val_unit);
 }
diff --git a/testu01/testu01/unif01_stubs.h b/testu01/testu01/unif01_stubs.h
index 09e07a0..91af9f7 100644
--- a/testu01/testu01/unif01_stubs.h
+++ b/testu01/testu01/unif01_stubs.h
@@ -12,8 +12,6 @@
 
 #include <unif01.h>
 
-static struct custom_operations unif01_Gen_boxed;
-
 #define IGNORE(x) (void)(x)
 #define unif01_Gen_unbox(bgen) (* (unif01_Gen**) Data_custom_val(bgen))