I’m working my way through an epic Rails 3.1 upgrade and some of my cucumber features were failing because I was using a custom RSpec matcher and the method wasn’t found.

My custom matcher looks something like this:

module CustomMatchers

  class XmlSubsetMatcher
      :
  end

  def be_xml_subset_of(expected)
    XmlSubsetMatcher.new(expected)
  end

and when I ran my feature I was getting this failure:

undefined method `xml_subset_of?' for # (NoMethodError)


As it turns out, in my zeal to make sure everything was using the latest and great new stuff, I had forgotten to move over this critical configuration line in cucumbers env.rb:


World(CustomMatchers)


Now, my cucumber feature is happily failing cuz my code doesn’t work. Whew. I couldn’t find this documented anywhere and I’m not even sure where this documentation would belong. I found a hint on the cucumber wiki rspec expectations page, but none of the code on that page is actually needed when using cucumber with Rails, so I decided not to touch it and just write this blog post.