@Test
    void monitorBlockingTaskExecutorAndSchedulersTogetherWithPrometheus() {
        final PrometheusMeterRegistry registry = PrometheusMeterRegistries.newRegistry();
        Metrics.addRegistry(registry);
        Server.builder()
              .meterRegistry(registry)
              .service("/", (ctx, req) -> HttpResponse.of(200))
              .build();
        Schedulers.enableMetrics();
        Schedulers.decorateExecutorService(Schedulers.single(), Executors.newSingleThreadScheduledExecutor());
    }
Makes sure that {@link ServerBuilder#decorator(DecoratingHttpServiceFunction)} works at every service and
virtual hosts and {@link VirtualHostBuilder#decorator(DecoratingHttpServiceFunction)} works only at
its own services.
core/src/test/java/com/linecorp/armeria/server/ServerBuilderTest.java