title: Factory Girl, Mongoid, and Embedded Documents
body: <p>I am setting up my first app with Mongoid and Devise. I am trying to Factory a user in my test with this factory:</p>
  
  <pre><code>Factory.define(:user) do |f|
    f.email "bob1234@example.com"
    f.password "testing"
    f.password_confirmation "testing"
  end
  </code></pre>
  
  <p>When I try and factory this I get this error:</p>
  
  <pre><code>NoMethodError: undefined method `add_on_blank' for []:Array
      from /Library/Ruby/Gems/1.8/gems/mongoid-2.0.1/lib/mongoid/criteria.rb:213:in `send'
      from /Library/Ruby/Gems/1.8/gems/mongoid-2.0.1/lib/mongoid/criteria.rb:213:in `method_missing'
      from /Library/Ruby/Gems/1.8/gems/mongoid-2.0.1/lib/mongoid/relations/embedded/many.rb:373:in `send'
      from /Library/Ruby/Gems/1.8/gems/mongoid-2.0.1/lib/mongoid/relations/embedded/many.rb:373:in `method_missing'
      from /Library/Ruby/Gems/1.8/gems/mongoid-2.0.1/lib/mongoid/named_scope.rb:121:in `with_scope'
      from /Library/Ruby/Gems/1.8/gems/mongoid-2.0.1/lib/mongoid/relations/embedded/many.rb:372:in `send'
      from /Library/Ruby/Gems/1.8/gems/mongoid-2.0.1/lib/mongoid/relations/embedded/many.rb:372:in `method_missing'
  </code></pre>
  
  <p>My models look like:</p>
  
  <p>User:</p>
  
  <pre><code>class User
    include Mongoid::Document
    # Include default devise modules. Others available are:
    # :token_authenticatable, :encryptable, :confirmable, :lockable, :timeoutable and :omniauthable
    devise :database_authenticatable, :registerable,
       :recoverable, :rememberable, :trackable, :validatable
  
    attr_accessible :email, :password, :password_confirmation, :remember_me
  
    embeds_many :errors
  end
  </code></pre>
  
  <p>Error:</p>
  
  <pre><code>class Error
    include Mongoid::Document
    field :klass, :type =&gt; String
    embedded_in :user
  end
  </code></pre>
  
  <p>How should a user model be created without creating any embedded documents at the same time?</p>