I mistaken included the "shoulda" gem in the "development" group. When generating cucumber with the following options I receive the following error:
rails g cucumber:install --capybara --rspec --spork
/Volumes/Data/Users/nicholas/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/1.9.1/minitest/unit.rb:566:in `block in process_args': invalid option: --capybara (OptionParser::InvalidOption) from /Volumes/Data/Users/nicholas/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/1.9.1/minitest/unit.rb:545:in `new' from /Volumes/Data/Users/nicholas/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/1.9.1/minitest/unit.rb:545:in `process_args' from /Volumes/Data/Users/nicholas/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/1.9.1/minitest/unit.rb:576:in `run' from /Volumes/Data/Users/nicholas/.rvm/rubies/ruby-1.9.2-p0/lib/ruby/1.9.1/minitest/unit.rb:492:in `block in autorun'
Excluding "shoulda" from the "development" group (i.e. just in test) resolved the error.