Run this manual test. It does display a dialog requiring to install one of two very specific printer models: either Lexmark E352dn PS3 or Dell 5310n -- and having a single enabled button "Start test".

A natural reaction of a tester would be -- perhaps I don't understand something -- to close this dialog using [x] decoration button, because she has no such printer to install.

Now, after that she could go for coffee since the test dialog is invisible and the test eventually fails with timeout.
BTW how much time does it take to install a printer?