Well, it depends on how fat he is, what injection site he's using, and how many mL's. If it's a really small amount per injection, like 1/2 mL, he's totally fine no matter what, as test E can be used subcutaneously. If it's a higher amount, then injection sites with less fat would be preferential, such as delts. I only use 5/8 myself, because I'm very lean, and that's a sufficient length for me at most sites. If your friend is fat, he should get some longer pins. I'm guessing he got insulin pins? That's the easiest thing to get over the counter. If he wants something else, he should order online.
Also, your 'friend' is you. We're not stupid.