diff --git a/tests/test-mdeque.c b/tests/test-mdeque.c
index 5251fc8c..e46555ee 100644
--- a/tests/test-mdeque.c
+++ b/tests/test-mdeque.c
@@ -36,6 +36,12 @@ DEQUE_DEF(deque_mpz, testobj_t, TESTOBJ_OPLIST)
 // Deque with the minimum number of methods.
 DEQUE_DEF(deque_min_z, testobj_t, (INIT_SET(testobj_init_set), SET(testobj_set), CLEAR(testobj_clear)))
 
+typedef enum {
+  SUCCESS = 0, NULL_PARAM, INVALID_PARAM
+} ReturnCode_t;
+
+DEQUE_DEF(deque_retcode, ReturnCode_t, M_ENUM_OPLIST(ReturnCode_t, SUCCESS))
+     
 #define OPL DEQUE_OPLIST(deque)
 
 static void test_ti1(int n)
@@ -276,12 +282,12 @@ static void test_io(void)
   M_LET(z, TESTOBJ_OPLIST)
   M_LET(str, STRING_OPLIST) {
     // Test empty
-    FILE *f = m_core_fopen ("a-marray.dat", "wt");
+    FILE *f = m_core_fopen ("a-mdeque.dat", "wt");
     if (!f) abort();
     deque_mpz_out_str(f, d1);
     fclose (f);
 
-    f = m_core_fopen ("a-marray.dat", "rt");
+    f = m_core_fopen ("a-mdeque.dat", "rt");
     if (!f) abort();
     bool b = deque_mpz_in_str (d2, f);
     assert (b == true);
@@ -294,12 +300,12 @@ static void test_io(void)
       deque_mpz_push_back (d1, z);
     }
   
-    f = m_core_fopen ("a-marray.dat", "wt");
+    f = m_core_fopen ("a-mdeque.dat", "wt");
     if (!f) abort();
     deque_mpz_out_str(f, d1);
     fclose (f);
     
-    f = m_core_fopen ("a-marray.dat", "rt");
+    f = m_core_fopen ("a-mdeque.dat", "rt");
     if (!f) abort();
     b = deque_mpz_in_str (d2, f);
     assert (b == true);
@@ -340,6 +346,44 @@ static void test_io(void)
   }
 }
 
+static void test_io_enum(void)
+{
+  deque_retcode_t d1, d2;
+  string_t s;
+
+  string_init(s);
+  deque_retcode_init(d1);
+  deque_retcode_init(d2);
+  
+  ReturnCode_t *ret = deque_retcode_push_back_new(d1);
+  assert( *ret == SUCCESS);
+  deque_retcode_push_front(d1, INVALID_PARAM);
+  
+  FILE *f = m_core_fopen ("a-mdeque.dat", "wt");
+  if (!f) abort();
+  deque_retcode_out_str(f, d1);
+  fclose (f);
+
+  f = m_core_fopen ("a-mdeque.dat", "rt");
+  if (!f) abort();
+  bool b = deque_retcode_in_str (d2, f);
+  assert (b == true);
+  assert (deque_retcode_equal_p (d1, d2));
+  fclose(f);
+
+  deque_retcode_get_str(s, d1, false);
+  assert (string_equal_str_p(s, "[2,0]"));
+
+  b = deque_retcode_parse_str(d2, string_get_cstr(s), NULL);
+  assert(b == true);
+  assert (deque_retcode_equal_p (d1, d2));
+  
+  string_clear(s);
+  deque_retcode_clear(d1);
+  deque_retcode_clear(d2);
+}
+
+
 int main(void)
 {
   test1();
@@ -350,6 +394,7 @@ int main(void)
   test_it();
   test_set();
   test_io();
+  test_io_enum();
   test_z();
   test_advance();
   exit(0);
diff --git a/tests/test-mserial-json.c b/tests/test-mserial-json.c
index 9c3fbadf..b42ad12f 100644
--- a/tests/test-mserial-json.c
+++ b/tests/test-mserial-json.c
@@ -43,7 +43,12 @@ VARIANT_DEF2(v2,
              (is_int, int),
              (is_bool, bool) )
 #define M_OPL_v2_t() VARIANT_OPLIST(v2, M_DEFAULT_OPLIST, M_DEFAULT_OPLIST)
-            
+
+typedef enum {
+  SUCCESS = 0, NULL_PARAM, INVALID_PARAM
+} my_return_code_t;
+#define M_OPL_my_return_code_t() M_ENUM_OPLIST(my_return_code_t, SUCCESS)
+
 TUPLE_DEF2(my,
            (vala, int),
            (valb, float),
@@ -52,9 +57,10 @@ TUPLE_DEF2(my,
            (vale, a2_t),
            (valf, v2_t),
            (valg, l2_t),
-           (valh, d2_t)
+           (valh, d2_t),
+           (vali, my_return_code_t)
            )
-#define M_OPL_my_t() TUPLE_OPLIST(my, M_DEFAULT_OPLIST, M_DEFAULT_OPLIST, M_DEFAULT_OPLIST, STRING_OPLIST, M_OPL_a2_t(), M_OPL_v2_t(), M_OPL_l2_t(), M_OPL_d2_t() )
+#define M_OPL_my_t() TUPLE_OPLIST(my, M_DEFAULT_OPLIST, M_DEFAULT_OPLIST, M_DEFAULT_OPLIST, STRING_OPLIST, M_OPL_a2_t(), M_OPL_v2_t(), M_OPL_l2_t(), M_OPL_d2_t(), M_OPL_my_return_code_t() )
 
 TUPLE_DEF2(my2,
            (activated, bool),
@@ -69,7 +75,7 @@ static void test_out_empty(void)
   my2_init(el1);
   my2_init(el2);
   
-  FILE *f = m_core_m_core_fopen ("a-mjson.dat", "wt");
+  FILE *f = m_core_fopen ("a-mjson.dat", "wt");
   if (!f) abort();
   m_serial_json_write_init(out, f);
   ret = my2_out_serial(out, el1);
@@ -77,15 +83,15 @@ static void test_out_empty(void)
   m_serial_json_write_clear(out);
   fclose(f);
 
-  f = m_core_m_core_fopen ("a-mjson.dat", "rt");
+  f = m_core_fopen ("a-mjson.dat", "rt");
   if (!f) abort();
-  static const char expected[] = "{ \"activated\":false,\"data\":{ \"vala\":0,\"valb\":0.000000,\"valc\":false,\"vald\":\"\",\"vale\":[],\"valf\":{},\"valg\":[],\"valh\":{}}";
+  static const char expected[] = "{ \"activated\":false,\"data\":{ \"vala\":0,\"valb\":0.000000,\"valc\":false,\"vald\":\"\",\"vale\":[],\"valf\":{},\"valg\":[],\"valh\":{},\"vali\":0}";
   char get[sizeof expected];
   fgets (get, sizeof expected , f);
   assert (strcmp(get, expected) == 0);
   fclose(f);
   
-  f = m_core_m_core_fopen ("a-mjson.dat", "rt");
+  f = m_core_fopen ("a-mjson.dat", "rt");
   if (!f) abort();
   m_serial_json_read_init(in, f);
   ret = my2_in_serial(el2, in);
@@ -108,7 +114,7 @@ static void test_out_fill(void)
   my2_init(el1);
   my2_init(el2);
   
-  FILE *f = m_core_m_core_fopen("a-mjson.dat", "wt");
+  FILE *f = m_core_fopen("a-mjson.dat", "wt");
   if (!f) abort();
   fprintf(f,
           "{\n"
@@ -121,10 +127,11 @@ static void test_out_fill(void)
           "\"valf\": { \"is_bool\": true },\n"
           "              \"vala\":1742,\n"
           " \"vald\": \"This is a test\",\n"
+          "\"vali\": 3,"
           "    \"valc\": true   } }\n");
   fclose(f);
 
-  f = m_core_m_core_fopen ("a-mjson.dat", "rt");
+  f = m_core_fopen ("a-mjson.dat", "rt");
   if (!f) abort();
   m_serial_json_read_init(in, f);
   ret = my2_in_serial(el2, in);
@@ -132,7 +139,7 @@ static void test_out_fill(void)
   m_serial_json_read_clear(in);
   fclose(f);
   
-  f = m_core_m_core_fopen ("a-mjson.dat", "wt");
+  f = m_core_fopen ("a-mjson.dat", "wt");
   if (!f) abort();
   m_serial_json_write_init(out, f);
   ret = my2_out_serial(out, el2);
@@ -140,16 +147,16 @@ static void test_out_fill(void)
   m_serial_json_write_clear(out);
   fclose(f);
 
-  f = m_core_m_core_fopen ("a-mjson.dat", "rt");
+  f = m_core_fopen ("a-mjson.dat", "rt");
   if (!f) abort();
-  static const char expected[] = "{ \"activated\":false,\"data\":{ \"vala\":1742,\"valb\":-2.300000,\"valc\":true,\"vald\":\"This is a test\",\"vale\":[1,2,3],\"valf\":{\"is_bool\":true},\"valg\":[1,2,3,4,5,6],\"valh\":{\"steeve\":-4,\"jane\":3}}}";
-  static const char expected2[] = "{ \"activated\":false,\"data\":{ \"vala\":1742,\"valb\":-2.300000,\"valc\":true,\"vald\":\"This is a test\",\"vale\":[1,2,3],\"valf\":{\"is_bool\":true},\"valg\":[1,2,3,4,5,6],\"valh\":{\"jane\":3,\"steeve\":-4}}}";
+  static const char expected[] = "{ \"activated\":false,\"data\":{ \"vala\":1742,\"valb\":-2.300000,\"valc\":true,\"vald\":\"This is a test\",\"vale\":[1,2,3],\"valf\":{\"is_bool\":true},\"valg\":[1,2,3,4,5,6],\"valh\":{\"steeve\":-4,\"jane\":3},\"vali\":3}}";
+  static const char expected2[] = "{ \"activated\":false,\"data\":{ \"vala\":1742,\"valb\":-2.300000,\"valc\":true,\"vald\":\"This is a test\",\"vale\":[1,2,3],\"valf\":{\"is_bool\":true},\"valg\":[1,2,3,4,5,6],\"valh\":{\"jane\":3,\"steeve\":-4},\"vali\":3}}";
   char get[sizeof expected];
   fgets (get, sizeof expected , f);
   assert (strcmp(get, expected) == 0 || strcmp(get, expected2) == 0);
   fclose(f);
   
-  f = m_core_m_core_fopen ("a-mjson.dat", "rt");
+  f = m_core_fopen ("a-mjson.dat", "rt");
   if (!f) abort();
   m_serial_json_read_init(in, f);
   ret = my2_in_serial(el1, in);