That's what I tend to do. I give someone my app, don't say a thing, and see how they attack it.
I like to think that the discoverability of my apps is good, but I can be surprised.
Just a couple of days ago, I got a request for help from my own timer app[0], that surprised me. They did not understand that the pickers were pickers. That's because I modified their appearance, so they look more like buttons. I'm still not exactly sure how I'll deal with it, but it's definitely my problem.