adds test for an API

test/test_option_type.py

@@ -75,6 +75,16 @@ def test_group_is_hidden():
         prop = err.proptype
     assert 'hidden' in prop
 
+def test_extend_properties():
+    descr = make_description()
+    config = Config(descr)
+    setting = config.cfgimpl_get_settings()
+    config.read_write()
+    gc = config.unwrap_from_path('gc')
+    config.unwrap_from_path('gc.dummy')
+    setting[gc].extend(['hidden', 'user_defined_property'])
+    assert 'hidden' in setting[gc]
+    assert 'user_defined_property' in setting[gc]
 
 def test_group_is_hidden_multi():
     descr = make_description()

tiramisu/setting.py

@@ -289,7 +289,7 @@ class Property(object):
         :param propnames: an iterable made of property names
         :type propnames: iterable of string
         """
-        for propname in propname:
+        for propname in propnames:
             self.append(propname)
 
     def reset(self):