This idea seems not a fantasy imagined by a few genius writers. In the 2016 Isaac Asimov Memorial Debate, Neil deGrasse Tyson, an astrophysicist said that we cannot dismiss this idea at all. Some other scientists agreed that it was possible, even not certain.
International Business Times: Neil deGrasse Tyson: Chances of universe being computer simulation 'may be very high'
The concept of a simulated world is fantastic. However, it is difficult to deny this hypothesis with a scientifically appropriate method. If the simulation is perfect, we have no idea to reveal it. There is a well-known theory named "Gödel's incompleteness theorems." Thus, every consistent system is unprovable within the system. Gödel's incompleteness theorems mentioned the natural number theory originally, but can apply to many other areas.
Lisa Randall, a physicist, opposed Tyson's idea in the debate. According to her, if our world were created by a computer programming, there would be several errors inevitably found. But I think it is not a rational counter for two reasons. First, "real human" having created our world may be able to write the perfect program. Second, there seem several errors called as miracles and mysteries observed all around the world.
After all, I think it is impossible for us to examine this concept on our own. We would be notified someday when someone in the outer world contact us directly.