The biggest upside compared to other code challenges I tried (HackerRank, CodinGame) is that the code is ran on your machine, and the pass/fails are from unit tests. So you code using your editors in a real development environment rather than in a web based sandbox.

Also, as the checks are from tests, there are no single right answer. I've seen some code challenge services (can't remember the name) that would mark fail if you didn't write it exactly as they were expecting, to the line break.