### Question:
HurlStack extends BaseHttpStack { static List<Header> convertHeaders(Map<String, List<String>> responseHeaders) { List<Header> headerList = new ArrayList<>(responseHeaders.size()); for (Map.Entry<String, List<String>> entry : responseHeaders.entrySet()) { if (entry.getKey() != null) { for (String value : entry.getValue()) { headerList.add(new Header(entry.getKey(), value)); } } } return headerList; } HurlStack();  HurlStack(UrlRewriter urlRewriter);  HurlStack(UrlRewriter urlRewriter, SSLSocketFactory sslSocketFactory); @Override HttpResponse executeRequest(Request<?> request, Map<String, String> additionalHeaders);  }### Answer:
@Test public void convertHeaders() { Map<String, List<String>> headers = new HashMap<>(); headers.put(null, Collections.singletonList("Ignored")); headers.put("HeaderA", Collections.singletonList("ValueA")); List<String> values = new ArrayList<>(); values.add("ValueB_1"); values.add("ValueB_2"); headers.put("HeaderB", values); List<Header> result = HurlStack.convertHeaders(headers); List<Header> expected = new ArrayList<>(); expected.add(new Header("HeaderA", "ValueA")); expected.add(new Header("HeaderB", "ValueB_1")); expected.add(new Header("HeaderB", "ValueB_2")); assertEquals(expected, result); }