"if you have to think about it and come up with a technicality about why you didn't really cheat, then you did."

Not that I advocate cheating, but that test bugs me. It seems to say "if it is possible to ask a discriminating question about whether or not cheating exists, then it exists", so unless a perfect (read: total) definition of cheating is set, there is always cheating!

I suspect that the root problem is the binary and lumped distinction "cheating/not cheating". It's likely better expressed as a set of boundaries, some of which may only be discovered post-hoc. The model of what constitutes cheating must be discovered and improved as a relationship continues.