private static void verifyHeaders(final WebSocketVersion version) throws Exception {
final SockJsConfig config = SockJsConfig.withPrefix("/echo").build();
final EmbeddedChannel ch = webSocketChannel(config);
final FullHttpRequest request = webSocketUpgradeRequest("/websocket", version);
ch.writeInbound(request);
final HttpResponse response = decode(ch);
assertThat(response.getStatus(), is(HttpResponseStatus.SWITCHING_PROTOCOLS));
assertThat(response.headers().get(CONNECTION), equalTo("Upgrade"));
assertThat(response.headers().get(UPGRADE), equalTo("websocket"));
assertThat(response.headers().get(CONTENT_LENGTH), is(nullValue()));