It is testing your Internet connection, but not the WiFi element, that would need some software installed on a device running the WiFi link.

So if your issue is intermitment Wi-Fi issues then this is not the right tool, but others such as http://www.thinkbroadband.com/speedtest would be more useful.

Yes seen the graph, and its so regular that its a bit of software kicking off a download or upload, or maybe the superhub doing some housekeeping

For some time I had the same problem. Bad connection in regular intervals. I could even hear faint noise with the quiet line test. Obviously there was some interference. I have set radio on my mobile phone to some quiet place with no station (AM medium range). All of the sudden I started to hear the regular noise. I thought "Got ya!" Now I can start looking for the source. I took me a while, but I found it. It turned out my old back boiler had faulty valve (the solenoid). Every time it burned gas, the valve was generating wide frequency noise.
My landlord agreed to replace for a modern high efficiency boiler. It was so old that no parts were available. My broadband was fixed and my gas bill went down. A win-win
What I want to say in this story is that you can't rule out anything, because it's unlikely. Use all your available resources and to get to the bottom of the problem.
Good luck!
sjz