@Test
  public void getAllHeaders() throws Exception {
    handler = new RequestHandler() {

      @Override
      public void handle(Request request, HttpServletResponse response) {
        response.setStatus(HTTP_OK);
        response.setHeader("a", "a");
        response.setHeader("b", "b");
        response.addHeader("a", "another");
      }
    };
    Map<String, List<String>> headers = get(url).headers();
    assertEquals(headers.size(), 5);
    assertEquals(headers.get("a").size(), 2);
    assertTrue(headers.get("b").get(0).equals("b"));
  }
Verify getting all headers

@throws Exception
lib/src/test/java/com/github/kevinsawicki/http/HttpRequestTest.java