How to test my GPIO code?
It doesn't appear that Onion release a full simulator for the Omega2, so there's no way you can "test" your GPIO code. Of course, you can get an idea of setting up and getting it to compile Ada code, but it won't be a real test. Even then, without hardware, a simulator protects you from the real world (no capacitance, no bad connections etc). Get started on getting the less well supported Ada toolchain up and running and expedite your hardware shipping!