@Test
void testGenerateLabels() {

   final Labeler labeler = new PrometheusLabeler();
   final Map<String, String> labels = labeler.generateLabels();
   
   assertThat(labels).size().isEqualTo(4);
   assertThat(labels).containsEntry(PrometheusLabeler.LABEL_PATH, PrometheusLabeler.DEFAULT_PATH);
   assertThat(labels).containsEntry(PrometheusLabeler.LABEL_PORT, PrometheusLabeler.DEFAULT_PORT);
   assertThat(labels).containsEntry(PrometheusLabeler.LABEL_SCHEME, PrometheusLabeler.DEFAULT_SCHEME);
   assertThat(labels).containsEntry(PrometheusLabeler.LABEL_SCRAPE, PrometheusLabeler.DEFAULT_SCRAPE);
}