Arduino Uno - Analog Circuit Simulator
You could use https://en.wikipedia.org/wiki/Ngspice.
From what is written there, the Xspice part could be used for creating a simple model of the Arduino, for checking how the analog part of your circuit interacts with the uC.
Unfortunately the main site () is down, atm, as many other projects hosted on SourceForge. But it might be worth having a look, once it's back online.