They seem to be necessary to build because check looks for them, but should R package suggestions also be RPM suggestions?

This sounds reasonable to me, maybe @spot could also weight in but otherwise
let's adjust this.
Though we'll likely need to make the distinction between Fedora and EPEL.

Well, this isn't an obvious answer. %check for the vast majority of things in CRAN checks for all possible features, above and being what is required for functionality of the addon, and this is why there are additional "suggests".

Strictly speaking, setting these as rpm suggests is correct, but...

Since dnf treats rpm suggests the same as requires (I think), this will make it a LOT harder to get any R packages generated with r2spec to get into Fedora (due to the much larger dependency chain). In fact, we end up disabling %check on a lot of new R packages for this exact reason. Oh, and there have been dependency loops that occur as a result of having %check enabled.

I think if we were to add these as rpm suggests, we should probably conditionalize them (and the tests in %check) so that it is easy to disable them.

R2spec already converts CRAN Suggests to rpm Requires and BuildRequires, so the dependency chain is already a problem...

Fixed by #23.