t2.save(self.db_conn)
self.assertEqual(Todo.by_date(self.db_conn, self.date1), [t1, t2])
self.assertEqual(Todo.by_date(self.db_conn, self.date2), [])
t2.save(self.db_conn)
self.assertEqual(Todo.by_date(self.db_conn, self.date1), [t1, t2])
self.assertEqual(Todo.by_date(self.db_conn, self.date2), [])