[stuaxo]

A huge amount of coding is reading code.

These tests don't test digging through code.

I've worked on projects where people role their own solutions instead of being able to use stuff that's out there and it's not great either.

The real solution I guess is talking to people and teasing this info out of them, and perhaps showing them some older code you have since fixed and seeing what they find in it.

Edit - one reason I personally try and use a lot of libraries is so that large parts of a project are maintained upstream after I leave my contract; the more I write into the project, the more the next dev will have to maintain, anything I can push back into external libraries is a win.