Funny you should ask. With my current employer, after the interview, I asked to see the code. My future manager took me upstairs to the location where the team was usually sitting. Surprised to see me, team leader was happy to oblige. I pulled up a chair, sat next to him and (while manager was standing by, watching), asked him to click through the codebase where I should be working if they hired me. I spent at least 20 minutes. When I was happy, I shook his hand and thanked him for showing me the code. I was happy with what I saw, accepted the offer and currently work there.
Tldr: ask to see the code. Interview them, its a two-way street.
Tldr: ask to see the code. Interview them, its a two-way street.