We are developing application level code that runs on an ARM processor. The BSP (low level code) is being delivered by a 3d party so our code sits just on top of this abstraction layer (code is written in c++).

To do unit testing, I assume we will have to mock/stub out the BSP library(essentially abstracting out the HW), but what I'm not sure of is if I write/run the unit test on my pc, do I compile it with for example GCC? Normally we use Realview compiler to compile our code for the ARM. Can I assume that if I compile and run the code with x86 compiler and the unit tests pass that it will also pass when compiled with RealView compiler?

I'm not sure how much difference the compiler makes and if you can trust that if the x86 compiled code pass the unit tests that you can also be confident that the Realview compiled code is ok.