@Override
    public void open() throws Exception {
        this.timerService =
                getInternalTimerService("processing timer", VoidNamespaceSerializer.INSTANCE, this);
        this.keySet = new HashSet<>();
        super.open();
    }
@Test
    void testProcessRecord() throws Exception {
        OutputTag<Long> sideOutputTag = new OutputTag<Long>("side-output") {};

        KeyedTwoOutputProcessOperator<Integer, Integer, Integer, Long> processOperator =
                new KeyedTwoOutputProcessOperator<>(
                        new TwoOutputStreamProcessFunction<Integer, Integer, Long>() {
                            @Override
                            public void processRecord(
                                    Integer record,
                                    Collector<Integer> output1,
                                    Collector<Long> output2,
                                    PartitionedContext ctx) {
                                output1.collect(record);
                                output2.collect((long) (record * 2));
                            }
                        },
                        sideOutputTag);

        try (KeyedOneInputStreamOperatorTestHarness<Integer, Integer, Integer> testHarness =
                new KeyedOneInputStreamOperatorTestHarness<>(
                        processOperator,
                        (KeySelector<Integer, Integer>) value -> value,
                        Types.INT)) {
            testHarness.open();
            testHarness.processElement(new StreamRecord<>(1));
            testHarness.processElement(new StreamRecord<>(2));
            testHarness.processElement(new StreamRecord<>(3));
            Collection<StreamRecord<Integer>> firstOutput = testHarness.getRecordOutput();
            ConcurrentLinkedQueue<StreamRecord<Long>> secondOutput =
                    testHarness.getSideOutput(sideOutputTag);
            assertThat(firstOutput)
                    .containsExactly(
                            new StreamRecord<>(1), new StreamRecord<>(2), new StreamRecord<>(3));
            assertThat(secondOutput)
                    .containsExactly(
                            new StreamRecord<>(2L), new StreamRecord<>(4L), new StreamRecord<>(6L));
        }
    }