### Question:
HttpService extends Service { public void addHeaders(Map<String, String> headersToAdd) { headers.putAll(headersToAdd); } 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 testAddHeaders() { String headerName1 = "customized_header1"; String headerValue1 = "customized_value1"; String headerName2 = "customized_header2"; String headerValue2 = "customized_value2"; HashMap<String, String> headersToAdd = new HashMap<>(); headersToAdd.put(headerName1, headerValue1); headersToAdd.put(headerName2, headerValue2); httpService.addHeaders(headersToAdd); assertTrue(httpService.getHeaders().get(headerName1).equals(headerValue1)); assertTrue(httpService.getHeaders().get(headerName2).equals(headerValue2)); }