Prepare the device and connection
Choose the device you expect to use most: Smart TV, Android TV, Apple TV, streaming box, mobile or computer. Update the operating system, restart the device and check available storage. Ethernet is the best baseline for a fixed television because temporary Wi-Fi problems can otherwise be confused with playback performance.
Run the speed test before the trial starts. Note download speed, ping and jitter, ideally both during the day and in the evening. A consistent result matters more than one high peak. If several people normally share the connection, test while the household is using it in a realistic way.