Complex systems and magic

I had an interesting interaction today with another team. We're using a system they're busy writing and maintaining and we're looking to become a tenant of theirs.That's cool. If you're writing a service you want people to use your service; it's one of the ways that you measure success of whatever project you're on.The problem is that it didn't work. Not only is it complex, it seems to be magical. In a bad way.I wrote some code that should have worked. I think it should have worked. A couple of my co-workers think it should have worked. The person from the team we're integrating with thinks it should work.But it doesn't.This then had a chilling effect. If something doesn't work that you think aught to, how do you know what works really works? More importantly, how do you explain what does work if you can't mentally place the "working" and "not working" ideas into different buckets?Magic is a dangerous thing in most systems. It's great when it's working, but when the magic stops working for whatever reason, it's awfully hard to fix.I'm not a fan of systems like that. It's a scary place to work in -- working through trial and error and not knowing what action work either make something work. Or not.