ws: send unsolicited pong control frame on connect in ws_test.v (#6010)

vlib/net/websocket/ws.v

@@ -590,6 +590,10 @@ pub fn (mut ws Client) read() int {
 	return -1
 }
 
+pub fn (mut ws Client) send_pong() int {
+	return ws.send_control_frame(.pong, 'PONG', [])
+}
+
 fn (mut ws Client) send_control_frame(code OPCode, frame_typ string, payload []byte) int {
 	mut bytes_written := -1
 	if ws.socket.sockfd <= 0 {

vlib/net/websocket/ws_test.v

@@ -41,7 +41,9 @@ fn ws_test(uri string) {
 	}
 }
 
-fn on_open(mut test Test, x voidptr, ws &websocket.Client) {
+fn on_open(mut test Test, x voidptr, mut ws &websocket.Client) {
+	// Send PONG only for testing porposes
+	ws.send_pong()
 	println('websocket opened.')
 	test.connected = true
 }