The tests might happen when the bw usage is high. One way would be to only do tests at night when it's low enough, but that wouldn't test when I actually need it.
Would be great if the speedtest checks would be done hourly and the solution would be an additional check. A simple http call to a service which if answered with 200 OK, the test can be done, otherwise skipped or delayed(configurable) by a specified amount of time(configurable).