Add tests for EmClass field overriding

tests/editorial_model/test_model.py

         field.uid = 'test field.'
         self.assertNotEqual(field.d_hash(), e_hash)
 
+    def test_field_override(self):
+        """ Test EmClass field overriding in inheritance """
+        cls1 = EmClass('testClass', 'test class')
+        cls1.new_field('test', data_handler = 'varchar', max_length = 8)
+        cls1.new_field('test2', data_handler = 'integer', nullable = True)
+
+        cls2 = EmClass('testClass2', parents = cls1)
+        cls2.new_field('test', data_handler = 'varchar', max_length = 16)
+        cls2.new_field('test2', data_handler = 'integer', nullable = False)
+
+        self.assertEqual(len(cls1.fields()), len(cls2.fields()))
+        self.assertEqual(cls1.fields('test').data_handler_options['max_length'], 8)
+        self.assertEqual(cls2.fields('test').data_handler_options['max_length'], 16)
+
+    ## @todo add more test when data handlers implements compatibility checks
+    def test_field_invalid_type_override(self):
+        """ Testing invalid fields overriding (incompatible data_handler)"""
+        cls1 = EmClass('testClass', 'test class')
+        cls1.new_field('test', data_handler = 'varchar', max_length = 8)
+        cls1.new_field('test2', data_handler = 'integer', nullable = True)
+
+        cls2 = EmClass('testClass2', parents = cls1)
+        with self.assertRaises(AttributeError):
+            cls2.new_field('test', data_handler = 'integer')
+
+    @unittest.skip("Wait for data handlers to implements a method to check options compatibility")
+    def test_field_invalid_options_overrid(self):
+        """ Testing invalid fields overriding (incompatible data handler options) """
+        cls1 = EmClass('testClass', 'test class')
+        cls1.new_field('test', data_handler = 'varchar', max_length = 8)
+        cls1.new_field('test2', data_handler = 'integer', nullable = True)
+
+        cls2 = EmClass('testClass2', parents = cls1)
+        with self.assertRaises(AttributeError):
+            cls2.new_field('test', data_handler = 'varchar', max_length = 2)
+
 class EmGroupTestCase(unittest.TestCase):
     
     def test_init(self):