@Override
    public void clean() {
        COUNTER_MAP.clear();
        GAUGE_MAP.clear();
        HISTOGRAM_MAP.clear();
    }
@Test
    public void testClean() throws Exception {
        prometheusMetricsRegister.clean();
        Field field1 = prometheusMetricsRegister.getClass().getDeclaredField("COUNTER_MAP");
        field1.setAccessible(true);
        Map<String, Counter> map1 = (Map<String, Counter>) field1.get(prometheusMetricsRegister);
        Assertions.assertTrue(CollectionUtils.isEmpty(map1));
        Field field2 = prometheusMetricsRegister.getClass().getDeclaredField("GAUGE_MAP");
        field2.setAccessible(true);
        Map<String, Gauge> map2 = (Map<String, Gauge>) field2.get(prometheusMetricsRegister);
        Assertions.assertTrue(CollectionUtils.isEmpty(map2));
        Field field3 = prometheusMetricsRegister.getClass().getDeclaredField("HISTOGRAM_MAP");
        field3.setAccessible(true);
        Map<String, Histogram> map3 = (Map<String, Histogram>) field3.get(prometheusMetricsRegister);
        Assertions.assertTrue(CollectionUtils.isEmpty(map3));
    }