One of the best speed test sites on the internet is called testmy.net. It allows you to do speed tests at any interval you choose to be performed in the background automatically. For example you could ask for a speed test to be performed every hour for 24 hours. At the end of that period it will generate a graph and a table telling you the results of each test. All the time intervals can be set as frequently and over whatever time period you want. This service is free. Of course, it also allows immediate one time only speed tests as well. I've been using it for years.