Probably you have already noticed that, but in Rails 3 got some new stuff going on. Same goes when testing Rails applications. Using is now deprecated so you'll probably need to change a whole bunch of tests and assertions. However, there is a quite fast way to do it. Open project in Netbeans and use Replace in project.

Go to Edit --> Replace in projects and type into corresponding fields:

Containing text: errors.on\((.+)\)\,
Replace With: errors\[$1\].first\,

Select "regular expression" and press find. Wait few seconds for the results and press replace.

After that rerun your tests:

rake test:all
# or if rspec
rake spec