### Question:
HttpResponseBuilder extends MutableContent { public HttpResponseBuilder setCacheControlMaxAge(long expirationTime) { String cacheControl = getHeader("Cache-Control"); List<String> directives = Lists.newArrayList(); if (cacheControl != null) { for (String directive : StringUtils.split(cacheControl, ',')) { directive = directive.trim(); if (!directive.startsWith("max-age") || StringUtils.split(directive, '=').length != 2) { directives.add(directive); } } } directives.add("max-age=" + expirationTime); setHeader("Cache-Control", StringUtils.join(directives, ',')); 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); HttpResponseBuilder addAllHeaders(Multimap<String, String> headers); Collection<String> removeHeader(String name); HttpResponseBuilder setCacheTtl(int cacheTtl); HttpResponseBuilder setExpirationTime(long expirationTime); HttpResponseBuilder setRefetchStrictNoCacheAfterMs(long refetchStrictNoCacheAfterMs); HttpResponseBuilder setCacheControlMaxAge(long expirationTime); HttpResponseBuilder setStrictNoCache(); HttpResponseBuilder setMetadata(String key, String value); HttpResponseBuilder setMetadata(Map<String, String> metadata); int getContentLength(); int getHttpStatusCode(); long getRefetchStrictNoCacheAfterMs();  }### Answer:
@Test public void setCacheControlMaxAge() { HttpResponseBuilder builder = new HttpResponseBuilder() .addHeader("Cache-Control", "public,max-age=100") .setCacheControlMaxAge(12345); Multimap<String, String> headers = builder.getHeaders(); assertEquals("public,max-age=12345", headers.get("Cache-Control").iterator().next()); }