I’ve been volunteering for some time now at a local hospital doing office work. Should I ask them for a testimonial even though they are not exactly a client, and I am not an official employee? –MM
By all means–get it and use it!
The best testimonials you can have are from those who know you and your work quite well.
Anyone who has experienced and has knowledge of your work and skill and what it’s like to work with you is a “client” and their testimonials are just as valid.