You can also use the test at http://dslreports.com/speedtest
This measures latency during the test, to see whether the latency changes during downloads and uploads.
DSLReports shows a dramatic change (increasing by several hundred msec) when I turn off my bufferbloat control (SQM/fq_codel) in my OpenWrt router. The thinkbroadband tester does not detect that increase.
If DSLReports shows bufferbloat, you should read the Bufferbloat site's "What do do about Bufferbloat?" at http://www.bufferbloat.net/projects/cerowrt/wiki/Wha...
Turning on fq_codel or installing OpenWrt in the router would work, or you may have to call your router vendor and ask when they will provide fq_codel in their firmware.