@VisibleForTesting
    int getPort() {
        Preconditions.checkState(httpServer != null, "Server has not been initialized.");
        return port;
    }
@Test
    void cannotStartTwoReportersOnSamePort() {
        assertThatThrownBy(
                        () ->
                                new PrometheusReporter(
                                        Collections.singleton(reporter.getPort()).iterator()))
                .isInstanceOf(Exception.class);
    }