public void addServer(HttpRequestHandler server, String hostname, int port, String pathPrefix) {
        Socket socket = new Socket(hostname, port);
        synchronized (this) {
            List<Handler> shandlers = handlers.get(socket);
            if (shandlers == null) {
                shandlers = new LinkedList<>();
                handlers.put(socket, shandlers);
            }
            shandlers.add(new Handler(server, pathPrefix));
        }
    }
Get an HTTP client that talks to this test transport layer.
clustercontroller-utils/src/test/java/com/yahoo/vespa/clustercontroller/utils/test/TestTransport.java