Added tests for the datahandler abstract class

lodel/leapi/datahandlers/base_classes.py

     ##@brief given a field type name, returns the associated python class
     # @param fieldtype_name str : A field type name (not case sensitive)
     # @return DataField child class
-    # @todo implements custom handlers fetch
     # @note To access custom data handlers it can be cool to prefix the handler name by plugin name for example ? (to ensure name unicity)
     @classmethod
     def from_name(cls, name):
         cls.load_base_handlers()
+        all_handlers = dict(cls._base_handlers, **cls.__custom_handlers)
         name = name.lower()
-        if name not in cls._base_handlers:
+        if name not in all_handlers:
             raise NameError("No data handlers named '%s'" % (name,))
-        return cls._base_handlers[name]
+        return all_handlers[name]
  
     ##@brief Return the module name to import in order to use the datahandler
     # @param data_handler_name str : Data handler name

tests/datahandlers/test_datahandler.py

 import unittest
 
 from lodel.leapi.datahandlers.base_classes import DataHandler
+from lodel.leapi.datahandlers.datas import Varchar
 
 
 class DataHandlerTestCase(unittest.TestCase):
         except NotImplementedError:
             self.assertNotIsInstance(datahandler, DataHandler)
             self.assertIsNone(datahandler)
-    
+
+    def test_register_new_handler(self):
+        DataHandler.register_new_handler('testvarchar', Varchar)
+        self.assertEqual(DataHandler.from_name('testvarchar'), Varchar)
+
+    def test_register_nonclass_as_handler(self):
+        try:
+            DataHandler.register_new_handler('testvarchar', 'common string')
+        except Exception as err:
+            self.assertEqual(ValueError, type(err))
+
+    def test_register_invalid_class_as_handler(self):
+
+        try:
+            DataHandler.register_new_handler('testvarchar', Exception)
+        except Exception as err:
+            self.assertEqual(ValueError, type(err))