def METHOD_NAME(self) -> None:
    num_vals = 1000
    datapipe = _DummyDataReader(num_vals)
    with patch("random.Random", new=lambda a: _FakeRandom(num_vals)):
        train_datapipe, val_datapipe = rand_split_train_val(datapipe, 0.8)
        self.assertEqual(len(list(train_datapipe)), num_vals * 0.8)
        self.assertEqual(len(list(val_datapipe)), num_vals * 0.2)
        self.assertEqual(
            len(set(train_datapipe).intersection(set(val_datapipe))), 0
        )