final HttpResponse response = xhrRequest(okRequest, echoFactory);
assertThat(response.getStatus(), is(HttpResponseStatus.OK));
SockJsTestUtil.assertCORSHeaders(response, "*");
assertThat(response.headers().get(ACCESS_CONTROL_ALLOW_HEADERS), equalTo("a, b, c"));
final String emptySessionUrl = echoFactory.config().prefix() + "/abc/" + UUID.randomUUID().toString();
final FullHttpRequest emptyHeaderRequest = httpRequest(emptySessionUrl + "/xhr", POST);
emptyHeaderRequest.headers().set(ACCESS_CONTROL_REQUEST_HEADERS, "");
final HttpResponse emptyHeaderResponse = xhrRequest(emptyHeaderRequest, echoFactory);
assertThat(emptyHeaderResponse.getStatus(), is(HttpResponseStatus.OK));
SockJsTestUtil.assertCORSHeaders(response, "*");