Tried it locally and it seems to work well. After checking what was the issue in add_three test (in the kata directly), it seems changing the compiler version to 1.66 fixes the issue. Another issue was the random tests performed with the rand crate, which needed to be updated as the rand::thread_rng().gen_range fn takes one argument (a range) instead of two arguments (which was the case in the past ig). I fixed everything in the fork.