Well so the reason I asked this questions is that I did screw up a bit, and I think it could have been caught had I done sufficient testing - but I didn't because it doesn't seem to be part of the culture here, and neither are peer reviews.
So I _was_ trying to do only what was asked of me, just writing the code, but I guess I thought what I did at my previous job could have helped - which is keeping track of what was needed and then how I planned to accomplish and test.
But yeah, you've got me thinking about how or whether I should broach this topic; I think my lead is great, seems open to ideas, wants things to work well, so maybe I'll just ask what they think about how to avoid these kinds of mistakes.