I was thinking it could work with [`g_test_skip`](https://docs.gtk.org/glib/func.test_skip.html) (_"Indicates that a test was skipped."_), like [used here](https://github.com/geany/geany/blob/2.0.0/tests/test_sidebar.c#L71). It looks like that isn't a GTK function, thus it should be safe to call.