I really like the assert{2.0} gem for testing and a first cut at debugging my Rails code. And many of the mix-in methods in Rails’ ActiveSupport gem make programming easier and the application friendlier. However, while integrating Sphinx/Ultrasphinx, a full-text search plugin, I discovered a nasty conflict between assert{2.0} and ActiveSupport, both define the method in_groups_of. Googling found nothing, posting on the rubyonrails-talk Google group turned up nothing so I dug into the code.
It appears that the assert{2.0} code is a subset of the functionality in the ActiveSupport code, so I just commented it out. So far, everything seems to work okay.