Is it possible to create an Apache or nginx server which simulates the response codes I want? If it is, how hard is to setup and accomplish that in Mac OS?
I don't know of any normal webserver that does that, but it's certainly possible to achieve that with mod_python:
This requires a little programming, but you just need to return appropriate code from the handler() function (which normally handles HTTP requests). I have quite often done this sort of stuff while web app programming and it just works.