Such tests are essential for me, not just to ensure compatibility, but to ensure that when Arcueid gets ported to a new architecture everything still works. This is the big problem I'm having now as I try to get Arcueid to run properly on 32-bit architectures.
I plan to break up the test suites for Arcueid into two, one involving low-level tests that are run via GNU Check (which we have today), and more high-level tests run by some putative unit testing framework, perhaps your own or something derived from it, that should run on any Arc implementation. I may spin out the latter set of test suites into a separate project of its own.