So how much should you reveal as a technical interviewer when the candidate decides to be the one asking the questions, and is there a good way to go about it?
For a company that's been working on something for 20 years and process is in bad shape it is a different thing. A new hire facing it is going have a harder time believing they can make a difference.
Every single one of them left within 3 months and they pretty much just used the time as paid interview prep. For one case in particular, they essentially just paid for this fellow to interview prep for an upcoming FB interview. And he stayed just long enough for the recruiter to get to keep their fee.
So it depends on your risk/reward trade off of this happening to you.
I want to hire people who see the problems as something they are comfortable dealing with and not a reason to leave the job.
If a candidate is asking about tests and documentation and process etc, it's likely because they have strong opinions on them. Let them know what it's like currently, and maybe what what the plan is, so they can decide if that's going to work for them. Personally, I'd ask about process because I enjoy being a cowboy, and a strict release process is not for me.
Of course, there's confidentiality and politeness with certain questions, e.g. often people ask why this seat is empty and you don't necessarily want to tell them that the last guy ragequit. But you also don't want to spin things. I often bring up Glassdoor reviews and it's common for people to spin excessive work as "a challenge".
If you're hiring someone smart (and you often want to!), they'll see right through it.
Also they shouldn't expect things to be perfect. If everything was 100% documented with full test coverage and everything is under control, why hire someone? That's a flag.
You don't need to go into full glorious detail either, but do not lie. Speak honestly about the issues in your organisation and what you're doing about them. Maybe the candidate can even add some value there. If you can't, that says a lot about your organisation. If you can't speak to a candidate about it, maybe you should speak on it internally.
Otherwise, you're likely gonna get the wrong people for the job or even worse you can turn an excellent hire into a resentful demoralised employee who feels cheated.
I've seen this exact thing playing out with a client I'm working with and they got double f*ked.. They hired the wrong person for the job and the person left the project worse off.
Your ideal candidate is going to be interested in solving those problems, and possibly have experience solving that kind of problem