Added an empty list return from parameter factories

Created by: stefanoborini

Small fix to return an empty list if the parameter_factories is undeclared. The default implementation should just return an empty list.

force_bdss/mco/tests/test_base_mco_factory.py

@@ -2,6 +2,7 @@ import unittest
 
 from traits.trait_errors import TraitError
 
+from force_bdss.mco.base_mco_factory import BaseMCOFactory
 from force_bdss.mco.tests.test_base_mco import DummyMCO
 from force_bdss.mco.tests.test_base_mco_communicator import \
     DummyMCOCommunicator
@@ -15,6 +16,23 @@ except ImportError:
 from envisage.plugin import Plugin
 
 
+class MCOFactory(BaseMCOFactory):
+    def get_identifier(self):
+        return "dummy_mco_2"
+
+    def get_name(self):
+        return "Dummy MCO 2"
+
+    def get_model_class(self):
+        return DummyMCOModel
+
+    def get_communicator_class(self):
+        return DummyMCOCommunicator
+
+    def get_optimizer_class(self):
+        return DummyMCO
+
+
 class TestBaseMCOFactory(unittest.TestCase):
     def setUp(self):
         self.plugin = mock.Mock(spec=Plugin, id="pid")
@@ -30,6 +48,10 @@ class TestBaseMCOFactory(unittest.TestCase):
         self.assertIsInstance(factory.create_model(),
                               DummyMCOModel)
 
+    def test_base_object_parameter_factories(self):
+        factory = MCOFactory(self.plugin)
+        self.assertEqual(factory.parameter_factories(), [])
+
     def test_broken_get_identifier(self):
         class Broken(DummyMCOFactory):
             def get_identifier(self):