@Test
public void testResolveExtraTagsFromRequestHeaders() {

    HttpHeaders headers = new HttpHeaders();
    headers.add("app", "demo");
    ServerRequest req = MockServerRequest.builder().headers(headers).build();
    Map<String, String> map = new HashMap<>();
    MetricImporterUtils.resolveExtraTagsFromRequestHeaders(req, map);
    Assert.assertEquals("demo", map.get("app"));
}