### Question:
HttpClient extends RestClient { public void addAdditionalHeader(String name, String value) { try { if (isNotBlank(name) && isNotBlank(value)) { headerMap.put(name, value); } else { log.warn("Not adding " + name + " to headers."); } } catch (Exception e) { logger.error(e.getMessage(), e); } } HttpClient(URL host, String contentType, ONAPComponentsList targetEntity);   HttpClient(URL host, String acceptType, String contentType, ONAPComponentsList targetEntity); @Override ONAPComponentsList getTargetEntity(); @Override void addBasicAuthHeader(String auth, String key); void addAdditionalHeader(String name, String value); void setAcceptType(String value);  }### Answer:
@Test public void testPost_nullHeader() throws MalformedURLException { wireMockRule.stubFor(post(urlEqualTo("/services/sdnc/post")) .willReturn(aResponse().withStatus(200).withHeader("Content-Type", "application/json").withBody(""))); URL url = new URL("http: HttpClient client = httpClientFactory.newJsonClient(url, ONAPComponents.BPMN); client.addAdditionalHeader("Accept", "application/json"); client.addAdditionalHeader("id", null); client.post("{}"); verify(exactly(1), postRequestedFor(urlEqualTo("/services/sdnc/post")).withHeader("Accept", equalTo("application/json"))); }