[bap]

You are now in the platform business.

I have to assume someone is using the software therefore there is some tribal knowledge of what it does? Otherwise this is maybe SAAS software that users use and some functionality is exposed that would allow you to begin decomposing backwards toward expected input/output. You're almost black-boxing at that point.

I will admit that I have, on very rare occasion, scream tested a piece of software running on a server that nobody would claim ownership or knowledge of either on the eng. team or within the org.

[potta_coffee]

There's a surface level understanding of what it does but nobody really understands how many of the large features really work, or what the actual rules are that govern them. Yes, much of this is black box. Example: yesterday I had to try to figure out what branch of code was compiled and deployed to our server. Everyone had assumed it was the Master branch, but no...deploying that branch fubared everything. I finally found the "working" branch of code.

[potta_coffee]

Part of the problem is that the people who owned tribal knowledge were all fired / quit without documenting anything. Every member of the existing team has been there around a year or less.