@Test
public void testQuit() {

    PrometheusExporter exporter = mock(PrometheusExporter.class);
    PrometheusMetric metric = new PrometheusMetric(null, null, exporter, "", false, false, false, false, false);
    metric.quit();
    // assertions
    verify(exporter, times(1)).flush();
    verify(exporter, times(1)).quit();
    // test null exporter
    metric = new PrometheusMetric(null, null, null, "", false, false, false, false, false);
    metric.quit();
    // no exceptions, and no actions
}