I always try to use an independent test rather than those provided by the isp.
I used: http://testmy.net/ which runs a series of 5 tests of random data download and upload to provide the results.
We have the 12mb option and I currently have 2 browser systems running 8 open window tabs (one browser is running my website stat visits on a permanent basis) on the desktop pc and my other half is playing an online game on the mini laptop over the WiFi connection.
