Include FileTest not working how I expect

Can someone explain the different ‘include’ behavior outlined in this
code snippet:

Is this a known difference between MRI/IronRuby in how include works?
Or is it a matter of different namespace clashes happening in

Can I make the code that works under MRI (calling unqualified exists?)
work in IronRuby?

The difference is that in Ruby the FileTest methods are both singleton
methods and private instance methods while in IronRuby they are just
singleton methods.
So this is a bug in FileTest. I’ll submit a fix.