Ask what development and code practices they use to increase code quality. It shows you care about code quality, and gives you the chance to say "ah yes, I've w

Ask what development and code practices they use to increase code quality. It shows you care about code quality, and gives you the chance to say "ah yes, I've worked with that", and ask "why nUnit and not xUnit" and "what did you find hardest to mock?" and "what percentage of your code goes through code review?" etc. followups. You'll also learn how they think about quality, and (via your followups) how they evaluate software and thus how they think in general.