What I did to get mongo_mapper and machinist to work with pickle.

adapter.rb

# spec/pickle/adapter.rb

module Pickle
  
  class Adapter
  
    class MongoMapper < Adapter
      def self.factories
        factories = []
        model_classes.each do |klass|
          if blueprints = klass.instance_variable_get('@blueprints')
            blueprints.keys.each {|blueprint| factories << new(klass, blueprint)}
          end
        end
        factories
      end
  
      def initialize(klass, blueprint)
        @klass, @blueprint = klass, blueprint
        @name = @klass.name.underscore.gsub('/','_')
        @name = "#{@blueprint}_#{@name}" unless @blueprint == :master
      end
  
      def create(attrs = {})
        @klass.send(:make, @blueprint, attrs)
      end
    end
  end
  
end

blueprints.rb

# spec/blueprints.rb
# include these in blueprints
# need machinist/mongo gem
require 'machinist/mongo_mapper'
require File.expand_path(File.dirname(__FILE__)) + "/pickle/adapter"
require File.expand_path(File.dirname(__FILE__)) + "/pickle/adapters/mongo_mapper"

env.rb

# features/support/env.rb

require File.dirname(__FILE__) + '/../../spec/blueprints' # or wherever your blueprints are
Before { Sham.reset } # to reset Sham's seed between scenarios so each run has same random sequences

require 'pickle/world'
# Example of configuring pickle:
#
Pickle.configure do |config|
  config.adapters = [MongoMapper]
  config.map 'I', 'myself', 'me', 'my', :to => 'user: "me"'
end

mongo_mapper.rb

# spec/pickle/adapters/mongo_mapper.rb


require 'mongo_mapper'

module MongoMapper
  module Document
    module PickleAdapter
      include Pickle::Adapter::Base

      # Do not consider these to be part of the class list
      def self.except_classes

      end

      # Gets a list of the available models for this adapter
      def self.model_classes
        @model_classes ||= Module.constants.inject([]) do |h, c|
          constant = eval(c)
          if !constant.nil? && constant.is_a?(Class) && constant.include?(MongoMapper::Document)
            h << constant
          end
          h
        end
      end

      # get a list of column names for a given class
      def self.column_names(klass)
        klass.column_names
      end

      # Get an instance by id of the model
      def self.get_model(klass, id)
        klass.find(id)
      end

      # Find the first instance matching conditions
      def self.find_first_model(klass, conditions)
        klass.first conditions
      end

      # Find all models matching conditions
      def self.find_all_models(klass, conditions)
        klass.all conditions
      end
    end
  end
end