WebSocketPolicy policy = WebSocketPolicy.newClientPolicy();
DeflateFrameExtension ext = new DeflateFrameExtension();
ext.setBufferPool(bufferPool);
ext.setPolicy(policy);
ext.setConfig(new ExtensionConfig(ext.getName()));
Generator generator = new Generator(policy, bufferPool, true);
generator.configureFromExtensions(Collections.singletonList(ext));
OutgoingNetworkBytesCapture capture = new OutgoingNetworkBytesCapture(generator);