Haven’t read it in years, so I don’t know that my opinion amounts to much.
My recollection is that they were pretty sloppy in their tests. Plus, testing a single firearm is pretty iffy anyway. Their results never seemed to match my own experiences.
More importantly, I always suspected ulterior motives on their part.
For example, if they reviewed an expensive Colt Python and an inexpensive Ruger revolver and reported that the Python was better, then a reader would say no big deal since the Colt costs more anyway. If they did this frequently, readers would start asking themselves why they even bothered buying the magazine.
However, by reporting that the cheap Ruger performed better than the expensive Colt, they also justified the purchase of their own magazine. If you check their sales literature, they make a big deal over such reports.
Regular gun rags are totally untrustworthy when reviewing firearms, but I’m not sure Guntests is really any better.
FWIW