### Question:
HttpResponse { public String header(String k) { List<String> vs = headers.get(k); return (vs == null || vs.isEmpty()) ? null : vs.get(0); } HttpResponse(int status, Map<String, List<String>> headers);  HttpResponse(int status, Map<String, List<String>> headers, byte[] data); int status(); Map<String, List<String>> headers(); String header(String k); Instant dateHeader(String k); byte[] entity(); String entityAsString(); HttpResponse decompress(); @Override String toString();  }### Answer:
@Test public void header() { Map<String, List<String>> headers = new HashMap<>(); headers.put("Content-Type", Collections.singletonList("application/json")); HttpResponse res = new HttpResponse(200, headers); Assertions.assertEquals("application/json", res.header("content-type")); Assertions.assertEquals("application/json", res.header("Content-Type")); }