add check for curtailment module in populated_correctly

Author: ahalev

tests/microgrid/test_microgrid.py

@@ -328,6 +328,9 @@ def set_microgrid(self):
     def test_populated_correctly(self):
         self.assertTrue(hasattr(self.microgrid.modules, 'load'))
         self.assertTrue(hasattr(self.microgrid.modules, 'renewable'))
+        self.assertTrue(hasattr(self.microgrid.modules, 'curtailment'))
+        self.assertEqual(len(self.microgrid.modules.curtailment), 1)
+
         self.assertEqual(len(self.microgrid.modules), self.n_modules)  # load, pv, unbalanced
 
     def test_current_load_correct(self):