as i can see in some .lua files in the game, `print` is used for debugging.

so can someone tell me, where is the output of those prints?

Tuner.

i added `print('test')` at the top of WorldView.lua
where will it printed?

or what is the other way to debug scripts?

When the modding tools are out, you will have a program running while you test/debug which is the target of the prints. Till then, it goes nowhere that you can see. (Well, it MIGHT display in the ~ menu, not sure there)