Does this still work on current versions of Ruby? The GitHub repo looks like it has a commit as recently as 3 months ago but the project hasn't made a release to Rubygems since 2017.
> We recommend using JRuby 9.X+, with the majority of our testing currently against 9.1. JRuby 1.7.x may work, but has been untested since 4.0.0.pre6.
Your question is still appropriate because they tested with 9,1 and JRuby is at 9.4
About MRI compatibility see https://github.com/shoes/shoes4/issues/1235