Here is what I think
- for code reuse. we can either inherit from common class(`ActiveSupport::Testing::Assertions`?) which would make this a public api OR make it a module which can be included in abstract units of all rails components. But making a module for just for 2 helper methods would be overkill. 
- Alternatively, if some code duplication is okay, we can paste following line in abstract unit of AS & AP


````ruby
%w[jruby rbx].each do |runtime|
  define_method("#{runtime}_skip") {|msg=''| skip msg if RUBY_ENGINE == runtime}
end
````
this would generate `jruby_skip` & `rbx_skip` methods. IMHO, this is the simplest approach & what I would like to do. so let me know if its okay, I will submit a PR.