I rarely get a true result using those online speedtest sites. I use the Firefox add-on
Broadband Speed Test and Diagnostics for Firefox.
1. Bandwidth measurement.
Open "Tools" menu and click the item "Bandwidth Meter". You can perform upload and download bandwidth measurement. It also shows your public IP address and public domain name.
2. Broadband troubleshooting.
When Firefox fails to load a webpage, the extension will automatically check whether Internet conennction is working or not. You can perform further diagnostic tests (ping, traceroute) or check the archived version of the failed webpage. Just try to type a non-existent domain name(e.g., qwqwqwq121212.com) to see this in action ...
3. Display local network configuration.
Use the diagnostic and configuration buttons to get local IP configurations (private IP address, MAC address, default gateway, DNS server, DHCP server, routing table, ARP table, active connections). This feature only works under Windows.