Factory Girl steps for Cucumber with MongoMapper: what about associations?

Update:

I tried to propagate the fix to Plucky itself, in vain. So far, it's not fixed. Use this patch, if you experience problems migrating your project from ActiveRecord to MongoMapper or MongoMapper problems not properly working with queries, even though the article is about FactoryGirl associations (which might've been changed in FactoryGirl itself by now).

I also came across hidden issues with MongoMapper, such as a method not working, but the test is designed in a way to pass. If it's my decision, I will try MongoId next time.

-------------------------

If you have an association (an Article belonging to a User) and you write something like that in Cucumber:

Given the following article exists:
 | title      | user                       |
 | My article | email: writer1@example.com |

then the Factory Girl steps will handle this association for you, creating both an Article and a User for your test if they are of the ActiveRecord class. But this will throw an exception with MongoMapper.

Digging into the Factory Girl steps code explains why. Factory Girl steps use User.find(:first, :conditions => attributes) but syntax such as find(:first...) doesn't exist for MongoMapper.

MongoMapper uses Plucky gem for all the find methods. I wrote the following monkey patch to account for the missing attributes:

/config/initializers/plucky_ext.rb
----------------------------------

Plucky::Query.class_eval do
alias_method :find_old, :find
def find_new(*args)
  options = args.extract_options!
  first = args.shift
  args.push(options)

  case first
     when :first
       first(*args)
     when :last
       last(*args)
     when :all
       all(*args)
     else
       args.unshift(first) unless first.nil?
       find_old(*args)
  end
end
alias_method :find, :find_new
end

Now the Factory Girl steps work with associations

MongoMapper with rspec/shoulda hack

As far as I know, MongoMapper is currently not able to handle association tests for rspec/shoulda, such as most common belongs_to, has_many, has_one. I think they are working on it, but it's not there yet.

I wrote a hack to work with MongoMapper, so far it's able to handle my simple belongs_to association, and my rspec test passes all right when it has the association and fails otherwise. As I progress through more associations, I will keep posting if it needs improvements.

In the config/initializers folder create a file mongo_mapper_ext.rb and place the following code into it:

module MongoMapperExt
  module Plugins
    module Associations           
      module ClassMethods      
        def reflect_on_association(association)
          associations[association].extend AssociationMethods if associations[association]
        end
      end
      module AssociationMethods
        def macro
          @macro = derive_macro
        end
        def primary_key_name
           @primary_key_name ||= options[:foreign_key] || derive_primary_key_name
        end
        def belongs_to?
          @macro == :belongs_to
        end
        
        private
         def derive_primary_key_name
          if belongs_to?
            "#{name}_id"
          elsif options[:as]
            "#{options[:as]}_id"
          else
            klass.foreign_key
          end
        end
        
        def derive_macro
          case self.class.name
            when "MongoMapper::Plugins::Associations::BelongsToAssociation"
                :belongs_to
            when "MongoMapper::Plugins::Associations::ManyAssociation"
                :has_many
            when "MongoMapper::Plugins::Associations::OneAssociation"
                :has_one
            else
              "unknown association"
          end
        end
      end
    end     
  end
end

MongoMapper::Document.send(:include, MongoMapperExt::Plugins::Associations)

Basically, it adds some methods from the ActiveRecord reflections which are missing in MongoMapper. Why not, if MongoMapper classes already contain suitable options to work with.