You do not get "high testosterone." Fapping does not affect your testosterone levels. It simply affects your libido. You beat your dick, you're satisfied, you calm down, you don't feel the need to do shit. You stop fapping your libido increases because we're programmed to mate, and you're not mating anymore (aka using your hand.) That libido can help with motivation and make you want to find someone to fuck, it's simple.
There is no scientific evidence showing testosterone increases or decreases with masturbation.