No one is aware of any family members being from any other country than the Philippines. I do know there is a town in England called TESTON but I am not aware of any links. Does anyone here have any links to the Philippines?
I am sure you must have checked that
How Filipinos Got Their Surnames
and don't forget that
The teston became the de facto unit of trade between Spaniards and Filipinos before the founding of Manila in 1574.
[Google is your friend ]
and 18,165 results for the Teston name on Geneanet