Re: "testimonial literature"
Hi minus273 and welcome to our forum!
I had to look around a little because "tanúirodalom" is not a current word in Hungarian - at least to my ears. (My personal first impression does not connect the word to eyewitnesses of horrible historical events specially but I suppose nowadays you cannot be "choosy"...)
However, it seems that it could be the one you are looking for because I have seen it in the sense you describe it in articles comparatively well written.
Nem az mutat tudósságot, aki sok nyelven beszél, hanem aki hasznos dolgokat tud mondani rajtuk. (Comenius)