### Question:
HttpResponseBuilder extends MutableContent { public HttpResponseBuilder addAllHeaders(Map<String, ? extends List<String>> headers) { for (Map.Entry<String,? extends List<String>> entry : headers.entrySet()) { this.headers.putAll(entry.getKey(), entry.getValue()); incrementNumChanges(); } return this; } HttpResponseBuilder(GadgetHtmlParser parser, HttpResponse response);  HttpResponseBuilder();  HttpResponseBuilder(HttpResponseBuilder builder);  HttpResponseBuilder(HttpResponse response); HttpResponse create(); HttpResponseBuilder setResponseString(String body); HttpResponseBuilder setEncoding(Charset charset); HttpResponseBuilder setResponse(byte[] responseBytes); HttpResponseBuilder setResponseNoCopy(byte[] responseBytes); HttpResponseBuilder setHttpStatusCode(int httpStatusCode); HttpResponseBuilder clearAllHeaders(); HttpResponseBuilder addHeader(String name, String value); HttpResponseBuilder setHeader(String name, String value); String getHeader(String name); HttpResponseBuilder addHeaders(Map<String, String> headers); HttpResponseBuilder addAllHeaders(Map<String, ? extends List<String>> headers); Collection<String> removeHeader(String name); HttpResponseBuilder setCacheTtl(int cacheTtl); HttpResponseBuilder setExpirationTime(long expirationTime); HttpResponseBuilder setStrictNoCache(); HttpResponseBuilder setMetadata(String key, String value); HttpResponseBuilder setMetadata(Map<String, String> metadata); int getContentLength(); int getHttpStatusCode();  }### Answer:
@Test public void addAllHeaders() { Map<String, List<String>> headers = Maps.newHashMap(); List<String> foo = Lists.newArrayList("bar", "blah"); List<String> bar = Lists.newArrayList("baz"); headers.put("foo", foo); headers.put("bar", bar); HttpResponseBuilder builder = new HttpResponseBuilder() .addAllHeaders(headers); assertTrue(builder.getHeaders().get("foo").containsAll(foo)); assertTrue(builder.getHeaders().get("bar").containsAll(bar)); }