@Test
public void testSetHeaders() {

  HttpHeaders headers = new HttpHeaders();
  Map<String, String> headersMap =
      ImmutableMap.of(
          "Custom-Header", "CustomHeader", "accept", "Accept", "Content-Length", "123");
  assertEquals(headers, HttpHeadersUtils.setHeaders(headers, headersMap));
  assertEquals("CustomHeader", headers.get("Custom-Header"));
  assertEquals("Accept", headers.getAccept());
  assertEquals(Long.valueOf(123L), headers.getContentLength());
}