Follow this link to download Siri Shortcut file that will simulate page loads in safari every 10 seconds. Useful for battery drain tests or Browser usage simulations.
Due to the nature of how this tests runs, it will use fairly large amounts of memory too so can double as a memory test of sorts.
I have updated the shortcut to also inform the user of the battery charge percentage at the start and end of the test.
For an in browser GPU rendering test I would recommend wirple.