On Sat, Jun 03, 2017 at 12:54:46AM +0200, Ludovic Courtès wrote:
> FAIL: grub_cmd_set_date
 
[...]

> All in all, I’m tempted to think this has to do with running the tests
> in parallel.
> 
> As a stop-gap measure, I’ve committed a change to run tests
> sequentially.  With this “guix build grub --rounds=5” passes for on my
> x86_64 laptop.  Let’s reopen the bug if we find that’s not enough.

This test just failed for me on x86_64, even with #:parallel-tests? #f.

So, perhaps it's not an inter-test race, or perhaps the tests are still
running in parallel, or some other thing.