@Override
    public void initializeState(StateInitializationContext context) throws Exception {
        super.initializeState(context);
        final ListState<byte[]> rawState =
                context.getOperatorStateStore().getListState(SPLITS_STATE_DESC);
        readerState = new SimpleVersionedListState<>(rawState, splitSerializer);
    }
@Test
    void testInitializeState() throws Exception {
        StateInitializationContext stateContext = context.createStateContext();
        operator.initializeState(stateContext);

        assertThat(
                        stateContext
                                .getOperatorStateStore()
                                .getListState(SourceOperator.SPLITS_STATE_DESC))
                .isNotNull();
    }