The WildFood festival use to be about rustic food that was at least occasionally eaten by people in the country. So of course testicles were a pretty common feature because there are a lot of farm animals who routinely have them removed, and--well--waste not, want not. Also many kind of wild animal and insect that most people would probably eat if they got stranded on an island out of reach of fried chicken.
But now it has officially crossed the line into just challenging people to eat the grossest thing that is not actually toxic, and charging them for the privilege. This year including shot glasses full of horse semen. This is not something any rugged bushman would turn to as a sensible source of food. It is offered purely for the gross out factor and is gross on many levels.
After all, if you eat lamb testicles you are symbolically taking on the role of a hardy farmer and wrangler who chops them off in the course of his calling. When you drink horse semen you are essentially taking on the role of the rubber vagina used by rich racehorse owners to wank off a scatter-brained luxury horse. That's kind of on the other end of the masculinity scale when you think about.