No, that you're blind to because it's in the nature of software development. Spotting flaws in something you've spent the last $X hours convincing yourself is c

No, that you're blind to because it's in the nature of software development. Spotting flaws in something you've spent the last $X hours convincing yourself is correct is hard to do. It's easy to make invalid assumptions and internalize them in your thinking to the point you don't notice them. This problem exists, and largely is solved by dragging in someone else to help with it. That someone else, unless you'd like to squabble over semantics, is doing QA.