I don't believe that syntax works going forward.  Updating the RSpec version to 3.0.0.beta1 and using that syntax yields:

    1) RailsBestPractices::Lexicals::RemoveTrailingWhitespaceCheck should remove trailing whitespace
        Failure/Error: expect(runner).to have(0).errors
        NoMethodError:
          undefined method `have' for #<RSpec::ExampleGroups::RailsBestPracticesLexicalsRemoveTrailingWhitespaceCheck:0x007fb104e285f8>
        # ./spec/rails_best_practices/lexicals/remove_trailing_whitespace_check_spec.rb:16:in `block (2 levels) in <module:Lexicals>'