+
+
+class TestModelState(unittest.TestCase):
+ def test_apply_delta(self):
+ from juju.model import Model
+ from juju.application import Application
+
+ loop = mock.MagicMock()
+ model = Model(loop=loop)
+ delta = _make_delta('application', 'add', dict(name='foo'))
+
+ # test add
+ prev, new = model.state.apply_delta(delta)
+ self.assertEqual(
+ len(model.state.state[delta.entity][delta.get_id()]), 1)
+ self.assertIsNone(prev)
+ self.assertIsInstance(new, Application)
+
+ # test remove
+ delta.type = 'remove'
+ prev, new = model.state.apply_delta(delta)
+ # length of the entity history deque is now 3:
+ # - 1 for the first delta
+ # - 1 for the second delta
+ # - 1 for the None sentinel appended after the 'remove'
+ self.assertEqual(
+ len(model.state.state[delta.entity][delta.get_id()]), 3)
+ self.assertIsInstance(new, Application)
+ # new object is falsy because its data is None
+ self.assertFalse(new)
+ self.assertIsInstance(prev, Application)
+ self.assertTrue(prev)