When the arduino's not plugged in (Processing)

I've got a Processing program that takes input from a bulky control box, run through an Arduino. I've currently got it set up to interface with an Arduino object through Firmata, and it's expecting (mainly) to be able to use analogRead and digitalRead to get input from a bank of sliders and buttons and things. It really shouldn't rely on having an arduino plugged in the whole time, though - I'd like to be able to work on it while the control box is stashed away, and it would be fun if there was an applet version for people to play with on the internet.

I wonder if there's a cunning way to make something like a decoy Arduino object so that the program doesn't fail, regardless? Or should I definitely just be fixing my program to expect something a bit more abstract, which may or may not be inputs from an arduino?

Or should I definitely just be fixing my program to expect something a bit more abstract, which may or may not be inputs from an arduino?

That sounds like the most logical way to go.