This is a very, very bad thought experiment. First of all, there need not be any discernible difference between fact and fiction, and so how exactly are you going to teach someone to be able to tell which is which without telling them?
'Cause this is what I imagined when I followed your instruction. Two different texts, one a description of real events that took place somewhere in the past, and another one a short fictional story entirely made up, but nevertheless not any different from the real one, barring details and such.
So what I'm saying is, you have to give us more to work with, or this is a very vague post that everyone's going to interpret in their own way and we're almost certainly not going to discuss what you had in mind.
'Cause this is what I imagined when I followed your instruction. Two different texts, one a description of real events that took place somewhere in the past, and another one a short fictional story entirely made up, but nevertheless not any different from the real one, barring details and such.
So what I'm saying is, you have to give us more to work with, or this is a very vague post that everyone's going to interpret in their own way and we're almost certainly not going to discuss what you had in mind.