Comment by lincolnq

If you're interested in this stuff at all, check out some code.

Example: https://github.com/ImperialCollegeLondon/FLT/blob/main/FLT/M...

Also check out the blueprint, which describes the overall structure of the code:

https://imperialcollegelondon.github.io/FLT/blueprint/

I'm very much an outside observer, but it is super interesting to see what Lean code looks like and how people contribute to it. Great thing is that there's no need for unittests (or, in some sense, the final proof statement is the unittest) :P