Within the MockIoAbstraction.h header there is an implementation of BasicIoAbstraction that delegates through a logging layer. If you are having difficulty determining what your code is sending and receiving, this could be useful.
This library itself is quite well tested using AUnit, and further it makes unit testing your code easier. There is a MockIoAbstraction that provides very easy support for mocking out an IoAbstraction.
There is a simulated version of task manager that can assist with getting hold of the registered tasks and a few other useful utility methods.
There is a simulated version of the EepromAbstraction, this uses a small amount of memory to store the state, to avoid writes to ROM during testing.
These Mock interfaces are fully documented in the reference docs.