When the auto speed test was first designed in 2010/2011, phones were still figuring things out.
Always, my goal with design is to make ONE thing that works with all browsers and devices. So I've always avoided apps. TestMy.net has never had an Android of iPhone app.
Now it's 2024, phones are a different breed. They are full fledged gaming PCs that make the desktop computers from 2010 look like a joke. In 2010 average RAM was 3-4GB. Now, our phones are coming out with 8-12GB!
The philosophy remains, ONE thing for them all.
For the auto test to work on any machine, not just Android, make sure the power remains on and the test in focus. On my S22 I normally have my display set to never turn off. I'm now noticing that they must have recently updated... now you can't set anything higher than 10 minutes.
That's alright, there's an app for that.
Screen Alive on Android does the trick. It's free with an option to donate to the developer.
Surprisingly, this isn't an issue on iOS. I would have thought if anyone did this it would be Apple. Android usually does things first but not things like this. On iOS just go do Display & Brightness > Auto Lock > Never.
Once your phone's display doesn't sleep anymore you can plug it into power and start up the auto test. Keep the browser in focus and it will do its thing.
Please let me know if this helps