Is GARP trivially satisfied with only 1 good? As with all revealed preference work, when the number of goods is greater than 1, then GARP (Generalised Axiom of Revealed Preference) is not always trivially satisfied. However, is it always the case that GARP is trivially satisfied when bundles only contain one good?

My take on it is that it is possible to violate GARP when the consideration set is only 1 good. However, empirically speaking, it should never be observed, as it really does not make sense from any rational point of view (ceteris paribus).  So theoretically, it is possible to violate GARP in a 1 good economy, but this is something we would never imagine observing.

(I've been having this discussion with a supervisor, and he seems to believe that GARP should never be violated with one good as it makes absolutely no sense for it to occur, despite my argument that it is theoretically possible)
I assume by "GARP" you mean "Generalized Axiom of Revealed Preference". One can take GARP to be satisfied with one good, but it's a rather vacuous type of "satisfied"; with one good the concept "preference" don't really have any meaning. You can't have any preferences if there's only one option.