### Question:
MetricRegistryImpl implements MetricRegistry { public boolean isShutdown() { synchronized (lock) { return isShutdown; } } MetricRegistryImpl(MetricRegistryConfiguration config); void startQueryService(ActorSystem actorSystem, ResourceID resourceID); @Override @Nullable String getMetricQueryServicePath(); @Override char getDelimiter(); @Override char getDelimiter(int reporterIndex); @Override int getNumberReporters(); @VisibleForTesting List<MetricReporter> getReporters(); boolean isShutdown(); CompletableFuture<Void> shutdown(); @Override ScopeFormats getScopeFormats(); @Override void register(Metric metric, String metricName, AbstractMetricGroup group); @Override void unregister(Metric metric, String metricName, AbstractMetricGroup group); @VisibleForTesting @Nullable ActorRef getQueryService();  }### Answer:
@Test public void testIsShutdown() throws Exception { MetricRegistryImpl metricRegistry = new MetricRegistryImpl(MetricRegistryConfiguration.defaultMetricRegistryConfiguration()); Assert.assertFalse(metricRegistry.isShutdown()); metricRegistry.shutdown().get(); Assert.assertTrue(metricRegistry.isShutdown()); }