The Ruby Spec Suite Compatibility Report

For a long time I wanted to show visually the compatibility of Ruby implementations with ruby/spec. This is not as easy as it sounds. First, we would like the same version of ruby/spec for all tested Ruby implementations, but in general each Ruby implementation uses a different version (except when synchronized once a month). We would like the same Ruby compatibility version (e.g., 2.6), but some Ruby implementations do not target 2.6 currently. And finally the number of specs (that is, of it examples) on a given platform should be fairly constant, which required a few fixes in ruby/spec.