Fast might be your first choice but it will obviously be a fine service if you want to check our Internet connection speed during anytime and it will provide you with top notch estimate of the metrics in
WiFi Speed Test quick seconds as well. One of the reasons why I would suggest to use this service for checking your speed is that they have a ping speed or latency of 3ms which is quite less compared to the 5ms from speedtest by Ookla.