def test_merge_last_updated_none(self):
        observer1 = LastValueAggregator()
        observer2 = LastValueAggregator()

        observer1.checkpoint = 23
        observer2.checkpoint = 47

        observer1.last_update_timestamp = 0
        observer2.last_update_timestamp = 100

        observer1.merge(observer2)

        self.assertEqual(observer1.checkpoint, 47)
        self.assertEqual(observer1.last_update_timestamp, 100)
    def test_merge_with_empty(self):
        observer1 = LastValueAggregator()
        observer2 = LastValueAggregator()

        observer1.checkpoint = 23
        observer1.last_update_timestamp = 100

        observer1.merge(observer2)

        self.assertEqual(observer1.checkpoint, 23)
        self.assertEqual(observer1.last_update_timestamp, 100)