The problem with prop drilling is often not the actual prop drilling, but that the component design is haphazard, so some props are coming from way up the tree, some from the next-highest state, and so on. It's hard to find where things are coming from because they're coming from everywhere.

What you're seeing as meticulously testing useless aspects of code is very likely just the end result of using the tests to design the code and make sure every use-case is thought out and verified (ie TDD).