Too much code in one place. Makes it hard to read the file and difficult to see what is code and what are tests. `wc` can no longer give you a quick approximation of code size either.
So I can keep a separate src/ and tests/ hierarchy? Why are the rust people so insistent on this even though most seen to want to could their test and src trees.
https://news.ycombinator.com/item?id=13791945