Testicle piercing in the sense of a permanent piece of jewelry which passes through the testicle is not possible. The anatomy, as well as the multiple layers/types of tissue involved, simply does not allow it. Attempting this piercing in the long term will simply result in a great deal of pain, and if you refuse to give up on it, infection and possibly castration or worse.
Again, to be clear: You can not get a permanent testicle piercing.
Now, a lot of people may tell you that they've seen these, and the photos above might give you an indication as to why an experienced piercer might make the assumption. But that "modification" is just temporary play (i.e. ball torture). Those not experienced with body piercing may also mistake a scrotal piercing or a transscrotal piercing for an actual testicle piercing.