I’ve not seen a caveat to who you can target with Testimony other than the target being in reach. Could you use Testimony on yourself? What about Anointing?
I believe that the answer is yes as long as you have a soul. There is nothing in the rules that stops you from being a legal target for your own effects, with the exception I believe of Physick where it is specifically called out.
For testimony you don’t even need to have the target consent, although drive by soul graffiti on the unwilling may get you anything from dirty looks to an inquisition, depending on what you apply and to whom.