CI check to enforce file level test coverage?

[sejori]

Ensure src files are adequately covered by units tests as CI check to maintain reliable code submissions? This could be annoying if we deliberately don't test some code.

[fergusfinn]

yeah good idea - we roughly have this but its not very visible. If you look at the rust ci it runs 'cargo llvm-cov' (there's a ts alternative). The metrics get reported here.

we had codecov before but it was a bit of a hassle