diff --git a/test/test_config.py b/test/test_config.py
index 3ac6edd..d66e27e 100644
--- a/test/test_config.py
+++ b/test/test_config.py
@@ -12,7 +12,7 @@ from tiramisu import Config
 from tiramisu.config import SubConfig
 from tiramisu.i18n import _
 from tiramisu import Config, IntOption, FloatOption, StrOption, ChoiceOption, \
-    BoolOption, UnicodeOption, OptionDescription, undefined
+    BoolOption, UnicodeOption, SymLinkOption, OptionDescription, undefined
 from tiramisu.error import ConflictError, ConfigError, PropertiesOptionError, APIError
 from tiramisu.storage import list_sessions
 
@@ -68,20 +68,13 @@ def test_base_config_name():
 #    assert raises(TypeError, "Config('str')")
 
 
-#def test_base_path():
-#    gcdummy = BoolOption('dummy', 'dummy', default=False)
-#    descr = OptionDescription('tiramisu', '', [gcdummy])
-#    cfg = Config(descr)
-#    assert cfg._impl_path is None
-#    base = OptionDescription('config', '', [descr])
-#    cfg = Config(base)
-#    assert cfg._impl_path is None
-#    assert cfg.getattr('tiramisu', None, validate_properties=False)._impl_path == 'tiramisu'
-#    nbase = OptionDescription('baseconfig', '', [base])
-#    cfg = Config(nbase)
-#    assert cfg._impl_path is None
-#    assert cfg.getattr('config', None, validate_properties=False)._impl_path == 'config'
-#    assert cfg.getattr('config.tiramisu', None, validate_properties=False)._impl_path == 'config.tiramisu'
+def test_base_path():
+    gcdummy = BoolOption('dummy', 'dummy', default=False)
+    descr = OptionDescription('tiramisu', '', [gcdummy])
+    Config(descr)
+    base = OptionDescription('config', '', [descr])
+    base
+    raises(ConfigError, "Config(base)")
 
 
 def test_base_config_force_permissive():
@@ -306,3 +299,40 @@ def test_config_subconfig():
     od2 = OptionDescription('od2', '', [od1])
     conf1 = Config(od2, session_id='conf1')
     raises(ConfigError, "conf2 = Config(od1, session_id='conf2')")
+
+
+def test_config_invalidsession():
+    i = IntOption('i', '')
+    o = OptionDescription('val', '', [i])
+    o2 = OptionDescription('val', '', [o])
+    raises(ValueError, 'Config(o2, session_id=2)')
+
+
+def test_config_od_name():
+    i = IntOption('i', '')
+    s = SymLinkOption('s', i)
+    o = OptionDescription('val', '', [i, s])
+    o2 = OptionDescription('val', '', [o])
+    c = Config(o2)
+    assert c.option('val.i').option.name() == 'i'
+    assert c.option('val.s').option.name() == 's'
+    assert c.option('val.s').option.name(follow_symlink=True) == 'i'
+
+
+def test_config_od_type():
+    i = IntOption('i', '')
+    o = OptionDescription('val', '', [i])
+    o2 = OptionDescription('val', '', [o])
+    c = Config(o2)
+    assert c.option('val.i').option.type() == 'integer'
+
+
+def test_config_default():
+    i = IntOption('i', '', 8)
+    o = OptionDescription('val', '', [i])
+    o2 = OptionDescription('val', '', [o])
+    c = Config(o2)
+    assert c.option('val.i').value.default() == 8
+    c.option('val.i').value.set(9)
+    assert c.option('val.i').value.get() == 9
+    assert c.option('val.i').value.default() == 8
diff --git a/test/test_config_ip.py b/test/test_config_ip.py
index 8532fe6..368d2eb 100644
--- a/test/test_config_ip.py
+++ b/test/test_config_ip.py
@@ -104,6 +104,7 @@ def test_network_cidr():
     cfg.option('a').value.set('0.0.0.0/0')
     raises(ValueError, "cfg.option('a').value.set('192.168.1.1')")
     raises(ValueError, "cfg.option('a').value.set('192.168.1.1/24')")
+    raises(ValueError, "cfg.option('a').value.set('2001:db00::0/24')")
 
 
 def test_network_invalid():
@@ -133,6 +134,7 @@ def test_broadcast():
     raises(ValueError, "cfg.option('a').value.set('192.168.0.300')")
     raises(ValueError, "cfg.option('a').value.set(1)")
     raises(ValueError, "cfg.option('a').value.set(2)")
+    raises(ValueError, "cfg.option('a').value.set('2001:db8::1')")
     cfg.option('a').value.set('0.0.0.0')
     cfg.option('a').value.set('255.255.255.0')
 
diff --git a/test/test_option.py b/test/test_option.py
index 7b9e556..a5e20d2 100644
--- a/test/test_option.py
+++ b/test/test_option.py
@@ -222,3 +222,8 @@ def test_intoption():
     cfg.option('test2').value.set(2)
     cfg.option('test2').value.set(3)
     raises(ValueError, "cfg.option('test2').value.set(4)")
+
+
+def test_get_display_type():
+    i1 = IntOption('test1', 'description', min_number=3)
+    assert i1.get_display_type() == 'integer'
diff --git a/test/test_option_setting.py b/test/test_option_setting.py
index 510af2c..6ba5cd5 100644
--- a/test/test_option_setting.py
+++ b/test/test_option_setting.py
@@ -82,6 +82,9 @@ def test_mod_read_only_write():
     config.property.setdefault(type='read_write', when='append', properties={'disabled',
                                                                              'hidden'})
     config.property.setdefault(type='read_write', when='remove', properties=set([]))
+    raises(ValueError, "config.property.setdefault(type='unknown', when='append', properties={'disabled'})")
+    raises(ValueError, "config.property.setdefault(type='read_only', when='unknown', properties={'disabled'})")
+    raises(TypeError, "config.property.setdefault(type='read_only', when='append', properties=['disabled'])")
 
     assert config.property.getdefault() == {'cache'}
     assert config.property.getdefault('read_only', 'append') == {'disabled'}
@@ -116,6 +119,8 @@ def test_mod_read_only_write():
                                                                    'everything_frozen',
                                                                    'mandatory',
                                                                    'empty'}
+    raises(ValueError, "config2.property.getdefault('unknown', 'remove')")
+    raises(ValueError, "config2.property.getdefault('read_write', 'unknown')")
 
 
 def test_setitem():
@@ -286,6 +291,7 @@ def test_apply_requires_from_config():
     raises(PropertiesOptionError, "api.option('opt.str').value.get()")
     assert 'hidden' in api.forcepermissive.option('opt.str').property.get()
     assert 'hidden' not in api.forcepermissive.option('opt.str').option.properties()
+    assert 'hidden' not in api.forcepermissive.option('opt.str').option.properties(only_raises=True)
 
 
 def test_apply_requires_with_disabled():
@@ -301,6 +307,7 @@ def test_apply_requires_with_disabled():
     api.option('int').value.set(1)
     raises(PropertiesOptionError, "api.option('opt.str').value.get()")
     assert 'disabled' not in api.unrestraint.option('opt.str').option.properties()
+    assert 'disabled' not in api.unrestraint.option('opt.str').option.properties(only_raises=True)
     assert 'disabled' in api.unrestraint.option('opt.str').property.get()
 
 
diff --git a/tiramisu/api.py b/tiramisu/api.py
index b428fd4..0ad6e65 100644
--- a/tiramisu/api.py
+++ b/tiramisu/api.py
@@ -148,11 +148,7 @@ class _TiramisuOptionOptionDescription(CommonTiramisuOption):
         return self._option_bag.option
 
     def type(self):
-        type_ = self._option_bag.option.__class__.__name__
-        if type_.endswith('Option'):
-            type_ = type_[:-6]
-        type_ = type_.lower()
-        return type_
+        return self._option_bag.option.get_display_type()
 
     def isleadership(self):
         """Test if option is a leader or a follower"""
@@ -659,29 +655,6 @@ class _TiramisuOptionDescription(_TiramisuOption):
                 return t_option
             ret.append(t_option)
         return ret
-#
-#    def get(self, name):
-#        self._get_option()
-#        current_option = self._option_bag.option.get_child(name,
-#                                                           self._config_bag,
-#                                                           self._subconfig.cfgimpl_get_path)
-#        path = self._option_bag.path + '.' + name
-#        option_bag= OptionBag()
-#        option_bag.set_option(current_option,
-#                              path,
-#                              None,
-#                              self._config_bag)
-#        if current_option.impl_is_optiondescription():
-#            subconfig = self._subconfig.getattr(name,
-#                                               option_bag)
-#        else:
-#            subconfig = self._subconfig
-#        return TiramisuOption(name,
-#                              path,
-#                              None,
-#                              subconfig,
-#                              self._config_bag,
-#                              option_bag)
 
     def group_type(self):
         """Get type for an optiondescription (only for optiondescription)"""
diff --git a/tiramisu/function.py b/tiramisu/function.py
index 8e19c76..46bf1c0 100644
--- a/tiramisu/function.py
+++ b/tiramisu/function.py
@@ -77,5 +77,5 @@ class ParamIndex(Param):
     __slots__ = tuple()
 
 
-def tiramisu_copy(val):
+def tiramisu_copy(val):  # pragma: no cover
     return val
diff --git a/tiramisu/option/baseoption.py b/tiramisu/option/baseoption.py
index 2591fd4..8f7d48e 100644
--- a/tiramisu/option/baseoption.py
+++ b/tiramisu/option/baseoption.py
@@ -18,7 +18,6 @@
 # the rough pypy's guys: http://codespeak.net/svn/pypy/dist/pypy/config/
 # the whole pypy projet is under MIT licence
 # ____________________________________________________________
-import re
 from types import FunctionType
 from typing import FrozenSet, Callable, Tuple, Set, Optional, Union, Any, List
 import weakref
@@ -36,14 +35,12 @@ STATIC_TUPLE = frozenset()
 
 
 submulti = 2
-NAME_REGEXP = re.compile(r'^[a-zA-Z][a-zA-Z\d_-]*$')
 
 
 def valid_name(name):
     if not isinstance(name, str):
         return False
     return True
-#    return re.match(NAME_REGEXP, name) is not None
 
 
 #____________________________________________________________
diff --git a/tiramisu/option/broadcastoption.py b/tiramisu/option/broadcastoption.py
index 04f3479..5e2a1e1 100644
--- a/tiramisu/option/broadcastoption.py
+++ b/tiramisu/option/broadcastoption.py
@@ -18,7 +18,7 @@
 # the rough pypy's guys: http://codespeak.net/svn/pypy/dist/pypy/config/
 # the whole pypy projet is under MIT licence
 # ____________________________________________________________
-from ipaddress import ip_address, IPv4Address, ip_network
+from ipaddress import ip_address, ip_network
 
 from ..error import ConfigError
 from ..setting import undefined, Undefined, OptionBag
@@ -42,8 +42,7 @@ class BroadcastOption(Option):
             if val.startswith("0") and len(val) > 1:
                 raise ValueError()
         try:
-            if not isinstance(ip_address(value), IPv4Address):
-                raise ValueError()
+            ip_address(value)
         except ValueError:
             raise ValueError()
 
diff --git a/tiramisu/option/domainnameoption.py b/tiramisu/option/domainnameoption.py
index d1ad2d9..1fc4d58 100644
--- a/tiramisu/option/domainnameoption.py
+++ b/tiramisu/option/domainnameoption.py
@@ -111,22 +111,14 @@ class DomainnameOption(StrOption):
 
         if not isinstance(value, str):
             raise ValueError(_('invalid string'))
-        if self.impl_get_extra('_allow_ip') is True:
-            try:
-                if not isinstance(ip_address(value), IPv4Address):
-                    raise ValueError()
-            except ValueError:
-                pass
-            else:
-                return
+        try:
+            ip_address(value)
+        except ValueError:
+            pass
         else:
-            try:
-                if not isinstance(ip_address(value), IPv4Address):
-                    raise ValueError()
-            except ValueError:
-                pass
-            else:
-                raise ValueError(_('must not be an IP'))
+            if self.impl_get_extra('_allow_ip') is True:
+                return
+            raise ValueError(_('must not be an IP'))
         part_name_length = self._get_len(self.impl_get_extra('_dom_type'))
         if self.impl_get_extra('_dom_type') == 'domainname':
             if not self.impl_get_extra('_allow_without_dot') and not "." in value:
diff --git a/tiramisu/option/ipoption.py b/tiramisu/option/ipoption.py
index a217c78..1412d59 100644
--- a/tiramisu/option/ipoption.py
+++ b/tiramisu/option/ipoption.py
@@ -18,7 +18,7 @@
 # the rough pypy's guys: http://codespeak.net/svn/pypy/dist/pypy/config/
 # the whole pypy projet is under MIT licence
 # ____________________________________________________________
-from ipaddress import ip_address, ip_interface, ip_network, IPv4Address, IPv4Interface
+from ipaddress import ip_address, ip_interface, ip_network
 
 from ..error import ConfigError
 from ..setting import undefined, Undefined, OptionBag
@@ -90,11 +90,9 @@ class IPOption(StrOption):
         # 'standard' validation
         try:
             if not cidr:
-                if not isinstance(ip_address(value), IPv4Address):
-                    raise ValueError()
+                ip_address(value)
             else:
-                if not isinstance(ip_interface(value), IPv4Address):
-                    raise ValueError()
+                ip_interface(value)
         except ValueError:
             raise ValueError()
 
diff --git a/tiramisu/option/networkoption.py b/tiramisu/option/networkoption.py
index 43e26f2..537021b 100644
--- a/tiramisu/option/networkoption.py
+++ b/tiramisu/option/networkoption.py
@@ -18,7 +18,7 @@
 # the rough pypy's guys: http://codespeak.net/svn/pypy/dist/pypy/config/
 # the whole pypy projet is under MIT licence
 # ____________________________________________________________
-from ipaddress import ip_address, ip_network, IPv4Network
+from ipaddress import ip_address, ip_network
 
 from ..setting import undefined
 from ..i18n import _
@@ -78,8 +78,7 @@ class NetworkOption(Option):
             if val.startswith("0") and len(val) > 1:
                 raise ValueError()
         try:
-            if not isinstance(ip_network(value), IPv4Network):
-                raise ValueError()
+            ip_network(value)
         except ValueError:
             raise ValueError()
 
diff --git a/tiramisu/option/option.py b/tiramisu/option/option.py
index ba0a1cb..38065d4 100644
--- a/tiramisu/option/option.py
+++ b/tiramisu/option/option.py
@@ -206,13 +206,7 @@ class Option(BaseOption):
 
     def impl_get_extra(self,
                        key: str) -> Any:
-        extra = getattr(self, '_extra', {})
-        if isinstance(extra, tuple):
-            if key in extra[0]:
-                return extra[1][extra[0].index(key)]
-            return None
-        else:
-            return extra.get(key)
+        return getattr(self, '_extra', {}).get(key)
 
     #__________________________________________________________________________
     # validator