diff --git a/test/test_option.py b/test/test_option.py
index 4b77356..1f4a340 100644
--- a/test/test_option.py
+++ b/test/test_option.py
@@ -6,8 +6,9 @@ do_autopath()
 
 from py.test import raises
 
-from tiramisu.error import APIError
+from tiramisu.error import APIError, ConfigError
 from tiramisu import IntOption, OptionDescription, Config
+from tiramisu.setting import groups
 
 
 def a_func():
@@ -113,6 +114,39 @@ def test_unknown_option():
     raises(AttributeError, "api.option('od.unknown.suboption').value.get()")
 
 
+def test_optiondescription_group():
+    groups.notfamily = groups.GroupType('notfamily')
+    i = IntOption('test', '')
+    i2 = IntOption('test', '')
+    od1 = OptionDescription('od', '', [i])
+    od1.impl_set_group_type(groups.family)
+    od3 = OptionDescription('od2', '', [i2])
+    od3.impl_set_group_type(groups.notfamily)
+    od2 = OptionDescription('od', '', [od1, od3])
+    api = Config(od2)
+    assert len(list(api.option.list('optiondescription'))) == 2
+    assert len(list(api.option.list('optiondescription', group_type=groups.family))) == 1
+    assert len(list(api.option.list('optiondescription', group_type=groups.notfamily))) == 1
+
+
+def test_optiondescription_group_redefined():
+    try:
+        groups.notfamily = groups.GroupType('notfamily')
+    except:
+        pass
+    i = IntOption('test', '')
+    od1 = OptionDescription('od', '', [i])
+    od1.impl_set_group_type(groups.family)
+    raises(ValueError, "od1.impl_set_group_type(groups.notfamily)")
+
+
+def test_optiondescription_group_masterslave():
+    i = IntOption('test', '')
+    od1 = OptionDescription('od', '', [i])
+    raises(ConfigError, "od1.impl_set_group_type(groups.master)")
+
+
+
 def test_asign_optiondescription():
     i = IntOption('test', '')
     od1 = OptionDescription('od', '', [i])
diff --git a/test/test_option_callback.py b/test/test_option_callback.py
index e520e3a..d1883f6 100644
--- a/test/test_option_callback.py
+++ b/test/test_option_callback.py
@@ -241,6 +241,20 @@ def test_callback_params_without_callback():
     raises(ValueError, "StrOption('val2', '', callback_params=Params(ParamValue('yes')))")
 
 
+def test_params():
+    raises(ValueError, "Params([ParamContext()])")
+    raises(ValueError, "Params('str')")
+    raises(ValueError, "Params(('str',))")
+    raises(ValueError, "Params(kwargs=[ParamContext()])")
+    raises(ValueError, "Params(kwargs={'a': 'str'})")
+
+
+def test_param_option():
+    val1 = StrOption('val1', "")
+    raises(ValueError, "ParamOption('str')")
+    raises(ValueError, "ParamOption(val1, 'str')")
+
+
 def test_callback_invalid():
     raises(ValueError, 'val1 = StrOption("val1", "", callback="string")')
     raises(ValueError, 'val1 = StrOption("val1", "", callback=return_val, callback_params="string")')
diff --git a/test/test_option_consistency.py b/test/test_option_consistency.py
index a37977b..d1054fb 100644
--- a/test/test_option_consistency.py
+++ b/test/test_option_consistency.py
@@ -415,6 +415,17 @@ def test_consistency_ip_netmask():
     api.option('b').value.set('255.255.255.0')
     raises(ValueError, "api.option('a').value.set('192.168.1.0')")
     raises(ValueError, "api.option('a').value.set('192.168.1.255')")
+    api.option('a').value.reset()
+    api.option('b').value.reset()
+    api.option('a').value.set('192.168.1.255')
+    raises(ValueError, "api.option('b').value.set('255.255.255.0')")
+
+
+def test_consistency_ip_netmask_invalid():
+    a = IPOption('a', '')
+    b = NetmaskOption('b', '')
+    od = OptionDescription('od', '', [a, b])
+    raises(ConfigError, "b.impl_add_consistency('ip_netmask')")
 
 
 def test_consistency_network_netmask():
@@ -431,6 +442,13 @@ def test_consistency_network_netmask():
     raises(ValueError, "api.option('a').value.set('192.168.1.1')")
 
 
+def test_consistency_network_netmask_invalid():
+    a = NetworkOption('a', '')
+    b = NetmaskOption('b', '')
+    od = OptionDescription('od', '', [a, b])
+    raises(ConfigError, "b.impl_add_consistency('network_netmask')")
+
+
 def test_consistency_ip_in_network():
     a = NetworkOption('a', '')
     b = NetmaskOption('b', '')
@@ -452,26 +470,13 @@ def test_consistency_ip_in_network():
     assert len(w) == 1
 
 
-# needs 3 arguments, not 2
-#def test_consistency_ip_in_network_len_error():
-#    a = NetworkOption('a', '')
-#    b = NetmaskOption('b', '')
-#    c = IPOption('c', '')
-#    od = OptionDescription('od', '', [a, b, c])
-#    raises(ConfigError, "c.impl_add_consistency('in_network', a)")
-
-
-# needs 2 arguments, not 3
-#def test_consistency_ip_netmask_network_error():
-#    a = IPOption('a', '')
-#    b = NetworkOption('b', '')
-#    c = NetmaskOption('c', '')
-#    od = OptionDescription('od', '', [a, b, c])
-#    c.impl_add_consistency('ip_netmask', a, b)
-#    api = Config(od)
-#    api.option('a').value.set('192.168.1.1')
-#    api.option('b').value.set('192.168.1.0')
-#    raises(ConfigError, "api.option('c').value.set('255.255.255.0')")
+def test_consistency_ip_in_network_invalid():
+    a = NetworkOption('a', '')
+    b = NetmaskOption('b', '')
+    c = IPOption('c', '')
+    d = IPOption('d', '')
+    od = OptionDescription('od', '', [a, b, c, d])
+    raises(ConfigError, "c.impl_add_consistency('in_network', a)")
 
 
 def test_consistency_ip_netmask_error_multi():
diff --git a/test/test_option_owner.py b/test/test_option_owner.py
index 2ae87ee..4dfefc5 100644
--- a/test/test_option_owner.py
+++ b/test/test_option_owner.py
@@ -112,6 +112,17 @@ def test_setowner_for_value():
     assert api.option('dummy').owner.get() == owners.new2
 
 
+def test_setowner_forbidden():
+    gcdummy = BoolOption('dummy', 'dummy', default=False)
+    descr = OptionDescription('tiramisu', '', [gcdummy])
+    api = Config(descr)
+    assert api.option('dummy').value.get() is False
+    assert api.option('dummy').owner.get() == 'default'
+    raises(ValueError, "api.owner.set('default')")
+    api.option('dummy').value.set(False)
+    raises(ValueError, "api.option('dummy').owner.set('default')")
+
+
 def test_setowner_read_only():
     gcdummy = BoolOption('dummy', 'dummy', default=False)
     descr = OptionDescription('tiramisu', '', [gcdummy])
diff --git a/tiramisu/option/broadcastoption.py b/tiramisu/option/broadcastoption.py
index 524fcef..ac0b662 100644
--- a/tiramisu/option/broadcastoption.py
+++ b/tiramisu/option/broadcastoption.py
@@ -49,7 +49,8 @@ class BroadcastOption(Option):
                         current_opt,
                         opts,
                         vals,
-                        warnings_only):
+                        warnings_only,
+                        context):
         if len(vals) != 3:
             raise ConfigError(_('invalid len for vals'))
         if None in vals:
diff --git a/tiramisu/option/choiceoption.py b/tiramisu/option/choiceoption.py
index d879c9b..a41cb93 100644
--- a/tiramisu/option/choiceoption.py
+++ b/tiramisu/option/choiceoption.py
@@ -85,7 +85,6 @@ class ChoiceOption(Option):
                         current_opt=undefined):
         if current_opt is undefined:
             current_opt = self
-        #FIXME cache? but in context...
         values = self._choice_values
         if isinstance(values, FunctionType):
             if option_bag is undefined:
diff --git a/tiramisu/option/ipoption.py b/tiramisu/option/ipoption.py
index 0299b5b..c2f4113 100644
--- a/tiramisu/option/ipoption.py
+++ b/tiramisu/option/ipoption.py
@@ -101,7 +101,10 @@ class IPOption(Option):
                          current_opt,
                          opts,
                          vals,
-                         warnings_only):
+                         warnings_only,
+                         context):
+        if len(vals) != 3 and context is undefined:
+            raise ConfigError(_('ip_network needs an IP, a network and a netmask'))
         if len(vals) != 3 or None in vals:
             return
         ip, network, netmask = vals
@@ -117,4 +120,5 @@ class IPOption(Option):
         opts[2]._cons_ip_netmask(current_opt,
                                  (opts[2], opts[0]),
                                  (netmask, ip),
-                                 warnings_only)
+                                 warnings_only,
+                                 context)
diff --git a/tiramisu/option/netmaskoption.py b/tiramisu/option/netmaskoption.py
index fb3b123..7f78d72 100644
--- a/tiramisu/option/netmaskoption.py
+++ b/tiramisu/option/netmaskoption.py
@@ -50,9 +50,12 @@ class NetmaskOption(Option):
                               current_opt,
                               opts,
                               vals,
-                              warnings_only):
+                              warnings_only,
+                              context):
         #opts must be (netmask, network) options
-        if len(vals) != 2 or None in vals:
+        if context is undefined and len(vals) != 2:
+            raise ConfigError(_('network_netmask needs a network and a netmask'))
+        if None in vals or len(vals) != 2:
             return
         return self.__cons_netmask(current_opt,
                                    opts,
@@ -66,9 +69,12 @@ class NetmaskOption(Option):
                          current_opt,
                          opts,
                          vals,
-                         warnings_only):
+                         warnings_only,
+                         context):
         #opts must be (netmask, ip) options
-        if len(vals) != 2 or None in vals:
+        if context is undefined and len(vals) != 2:
+            raise ConfigError(_('ip_netmask needs an IP and a netmask'))
+        if None in vals or len(vals) != 2:
             return
         self.__cons_netmask(current_opt,
                             opts,
@@ -86,8 +92,6 @@ class NetmaskOption(Option):
                        make_net,
                        warnings_only,
                        typ):
-        if len(opts) != 2:
-            raise ConfigError(_('invalid len for opts'))
         msg = None
         try:
             ip = IP('{0}/{1}'.format(val_ipnetwork, val_netmask), make_net=make_net)
@@ -99,7 +103,7 @@ class NetmaskOption(Option):
                         msg = _('this is a network with netmask "{0}" ("{1}")')
                     else:
                         msg = _('this is a network with {2} "{0}" ("{1}")')
-                if ip.broadcast() == val_ip:
+                elif ip.broadcast() == val_ip:
                     if current_opt == opts[1]:
                         msg = _('this is a broadcast with netmask "{0}" ("{1}")')
                     else:
diff --git a/tiramisu/option/option.py b/tiramisu/option/option.py
index 04a990d..1592ca8 100644
--- a/tiramisu/option/option.py
+++ b/tiramisu/option/option.py
@@ -207,8 +207,9 @@ class Option(OnlyOption):
             return
 
         def _is_not_unique(value):
-            #FIXME pourquoi la longueur doit etre egal ?
-            if check_error and self.impl_is_unique() and len(set(value)) != len(value):
+            # if set(value) has not same length than value
+            if check_error and self.impl_is_unique() and \
+                    len(set(value)) != len(value):
                 for idx, val in enumerate(value):
                     if val in value[idx+1:]:
                         raise ValueError(_('invalid value "{}", this value is already in "{}"'
@@ -243,7 +244,6 @@ class Option(OnlyOption):
             if isinstance(_value, list):  # pragma: no cover
                 raise ValueError(_('which must not be a list').format(_value,
                                                                       self.impl_get_display_name()))
-            #FIXME a revoir ...
             if _value is not None:
                 if check_error:
                     # option validation
@@ -271,8 +271,6 @@ class Option(OnlyOption):
                                                    self.__class__.__name__, 0)
                         else:
                             raise err
-        #if is_multi is None:
-        #    is_multi = self.impl_is_multi()
         try:
             val = value
             if not self.impl_is_multi():
@@ -332,8 +330,6 @@ class Option(OnlyOption):
         return False
 
     def impl_is_master_slaves(self, type_='both'):
-        """FIXME
-        """
         master_slaves = self.impl_get_master_slaves()
         if master_slaves is not None:
             if type_ in ('both', 'master') and \
@@ -654,7 +650,8 @@ class Option(OnlyOption):
                 getattr(self, func)(current_opt,
                                     all_cons_opts,
                                     values,
-                                    warnings_only)
+                                    warnings_only,
+                                    context)
         except ValueError as err:
             if warnings_only:
                 msg = _('attention, "{0}" could be an invalid {1} for "{2}", {3}'
@@ -672,7 +669,8 @@ class Option(OnlyOption):
                         current_opt,
                         opts,
                         vals,
-                        warnings_only):
+                        warnings_only,
+                        context):
         equal = []
         is_current = False
         for idx_inf, val_inf in enumerate(vals):
diff --git a/tiramisu/option/optiondescription.py b/tiramisu/option/optiondescription.py
index c9032ce..5a25e47 100644
--- a/tiramisu/option/optiondescription.py
+++ b/tiramisu/option/optiondescription.py
@@ -74,6 +74,15 @@ class CacheOptionDescription(BaseOption):
                 if not option.impl_is_symlinkoption():
                     properties = option.impl_getproperties()
                     if 'force_store_value' in properties:
+                        if option.impl_is_master_slaves('slave'):
+                            # problem with index
+                            raise ConfigError(_('the slave "{0}" cannot have '
+                                                '"force_store_value" property').format(
+                                                    option.impl_get_display_name()))
+                        if option.issubdyn():
+                            raise ConfigError(_('the dynoption "{0}" cannot have '
+                                                '"force_store_value" property').format(
+                                                    option.impl_get_display_name()))
                         force_store_values.append((subpath, option))
                     if 'force_default_on_freeze' in properties and \
                             'frozen' not in properties and \
@@ -163,15 +172,6 @@ class CacheOptionDescription(BaseOption):
         value_setted = False
         values = context.cfgimpl_get_values()
         for subpath, option in self._cache_force_store_values:
-            if option.impl_is_master_slaves('slave'):
-                # problem with index
-                raise ConfigError(_('the slave "{0}" cannot have '
-                                    '"force_store_value" property').format(
-                                        option.impl_get_display_name()))
-            if option.issubdyn():
-                raise ConfigError(_('the dynoption "{0}" cannot have '
-                                    '"force_store_value" property').format(
-                                        option.impl_get_display_name()))
             if not values._p_.hasvalue(subpath):
                 config_bag = ConfigBag(context=context)
                 option_bag = OptionBag()
@@ -429,12 +429,6 @@ class OptionDescription(OptionDescriptionWalk):
     def impl_getdoc(self):
         return self.impl_get_information('doc')
 
-    def impl_validate(self,
-                      *args,
-                      **kwargs):
-        """usefull for OptionDescription"""
-        pass
-
     # ____________________________________________________________
     def impl_set_group_type(self,
                             group_type):
@@ -444,8 +438,8 @@ class OptionDescription(OptionDescriptionWalk):
                               that lives in `setting.groups`
         """
         if self._group_type != groups.default:
-            raise TypeError(_('cannot change group_type if already set '
-                              '(old {0}, new {1})').format(self._group_type,
+            raise ValueError(_('cannot change group_type if already set '
+                               '(old {0}, new {1})').format(self._group_type,
                                                            group_type))
         if not isinstance(group_type, groups.GroupType):
             raise ValueError(_('group_type: {0}'
diff --git a/tiramisu/setting.py b/tiramisu/setting.py
index d7ecce4..af2d3b0 100644
--- a/tiramisu/setting.py
+++ b/tiramisu/setting.py
@@ -785,6 +785,9 @@ class Settings(object):
     def setowner(self,
                  owner):
         ":param owner: sets the default value for owner at the Config level"
+        if owner in forbidden_owners:
+            raise ValueError(_('set owner "{0}" is forbidden').format(str(owner)))
+
         self._owner = owner
 
     def getowner(self):
diff --git a/tiramisu/storage/util.py b/tiramisu/storage/util.py
index 26fee32..49d6977 100644
--- a/tiramisu/storage/util.py
+++ b/tiramisu/storage/util.py
@@ -19,7 +19,7 @@ from time import time
 from .cache.dictionary import Cache as DictCache
 
 
-def _display_classname(obj):
+def _display_classname(obj):  # pragma: no cover
     return(obj.__class__.__name__.lower())
 
 DEBUG = False
@@ -38,12 +38,12 @@ class Cache(DictCache):
         if slave, add index
         """
         if 'cache' in props or 'cache' in self_props:
-            if DEBUG:
+            if DEBUG:  # pragma: no cover
                 print('setcache {} with index {} and value {} in {} ({})'.format(path, index, val,
                                                                                  _display_classname(self),
                                                                                  id(self)))
             self._setcache(path, index, val, time())
-        elif DEBUG:
+        elif DEBUG:  # pragma: no cover
             print('not setcache {} with index {} and value {} and props {} and {} in {} ({})'.format(path,
                                                                                                      index,
                                                                                                      val,
@@ -60,7 +60,7 @@ class Cache(DictCache):
                  self_props,
                  type_):
         no_cache = False, None
-        if 'cache' in props:
+        if 'cache' in props or type_ == 'context_props':
             indexed = self._getcache(path, index)
             if indexed is None:
                 return no_cache
@@ -79,22 +79,22 @@ class Cache(DictCache):
                          'expire' in self_props):
                     ntime = int(time())
                     if timestamp + expires_time >= ntime:
-                        if DEBUG:
+                        if DEBUG:  # pragma: no cover
                             print('getcache in cache (1)', path, value, _display_classname(self),
                                   id(self), index)
                         return True, value
                     else:
-                        if DEBUG:
+                        if DEBUG:  # pragma: no cover
                             print('getcache expired value for path {} < {}'.format(
                                 timestamp + expires_time, ntime))
                         # if expired, remove from cache
                         #self.delcache(path)
                 else:
-                    if DEBUG:
+                    if DEBUG:  # pragma: no cover
                         print('getcache in cache (2)', path, value, _display_classname(self),
                               id(self), index)
                     return True, value
-        if DEBUG:
+        if DEBUG:  # pragma: no cover
             print('getcache {} with index {} not in {} cache'.format(path, index,
                                                                      _display_classname(self)))
         return no_cache
@@ -102,14 +102,14 @@ class Cache(DictCache):
     def delcache(self, path):
         """remove cache for a specified path
         """
-        if DEBUG:
+        if DEBUG:  # pragma: no cover
             print('delcache', path, _display_classname(self), id(self))
         if path in  self._cache:
             self._delcache(path)
 
     def reset_all_cache(self):
         "empty the cache"
-        if DEBUG:
+        if DEBUG:  # pragma: no cover
             print('reset_all_cache', _display_classname(self), id(self))
         self._reset_all_cache()
 
@@ -118,6 +118,6 @@ class Cache(DictCache):
         please only use it in test purpose
         example: {'path1': {'index1': ('value1', 'time1')}, 'path2': {'index2': ('value2', 'time2', )}}
         """
-        if DEBUG:
+        if DEBUG:  # pragma: no cover
             print('get_chached {} for {} ({})'.format(self._cache, _display_classname(self), id(self)))
         return self._get_cached()
diff --git a/tiramisu/value.py b/tiramisu/value.py
index ad0c8a3..7451e61 100644
--- a/tiramisu/value.py
+++ b/tiramisu/value.py
@@ -109,19 +109,11 @@ class Values(object):
                                          owners.default,
                                          index=_index,
                                          with_value=True)
-
-        if owner != owners.default:
+        if owner != owners.default and not ('frozen' in option_bag.properties and \
+                'force_default_on_freeze' in option_bag.properties):
             # if a value is store in storage, check if not frozen + force_default_on_freeze
             # if frozen + force_default_on_freeze => force default value
-            if not ('frozen' in option_bag.properties and \
-                    'force_default_on_freeze' in option_bag.properties):
-                if index is not None and not is_slave:
-                    if len(value) > index:
-                        return value[index]
-                    #value is smaller than expected
-                    #so return default value
-                else:
-                    return value
+            return value
         return self.getdefaultvalue(option_bag)
 
     def getdefaultvalue(self,
@@ -415,7 +407,7 @@ class Values(object):
             raise ConfigError(_("can't set owner for the symlinkoption \"{}\""
                                 "").format(opt.impl_get_display_name()))
         if owner in forbidden_owners:
-            raise ConfigError(_('set owner "{0}" is forbidden').format(str(owner)))
+            raise ValueError(_('set owner "{0}" is forbidden').format(str(owner)))
 
         if not self._p_.hasvalue(option_bag.path):
             raise ConfigError(_('no value for {0} cannot change owner to {1}'