### Question:
HttpService extends Service { public void addHeader(String key, String value) { headers.put(key, value); } HttpService(String url, OkHttpClient httpClient, boolean includeRawResponses);  HttpService(OkHttpClient httpClient, boolean includeRawResponses); private  HttpService(String url, OkHttpClient httpClient);  HttpService(String url);  HttpService(String url, boolean includeRawResponse);  HttpService(OkHttpClient httpClient);  HttpService(boolean includeRawResponse);  HttpService(); void addHeader(String key, String value); void addHeaders(Map<String, String> headersToAdd); HashMap<String, String> getHeaders(); static void setDebug(boolean debug); @Override void close(); static final MediaType JSON_MEDIA_TYPE; static final String DEFAULT_URL; }### Answer:
@Test public void testAddHeader() { String headerName = "customized_header0"; String headerValue = "customized_value0"; httpService.addHeader(headerName, headerValue); assertTrue(httpService.getHeaders().get(headerName).equals(headerValue)); }