Definitely--when working solo I tend to only write tests for things I actually want to run in isolation (and usually just to save time running the full codebase

Definitely--when working solo I tend to only write tests for things I actually want to run in isolation (and usually just to save time running the full codebase) or to establish some concrete expectations that I need to be aware of changes to (e.g. specific user scenarios that are critical to the thing working). These tend to overlap a lot.