post.rb

class Post
  include DataMapper::Resource
  
  property :id,       Serial
  property :title,    String
  property :content,  Text
  property :created_at, DateTime
  property :updated_at, DateTime

  validates_length :title, :min => 5

  belongs_to :author, :class_name => 'User'
end

post_spec.rb

describe Post do

  before(:each) do
    @user = create_default_user
    @valid_attributes = {
      :title => "Dude where is my car",
      :content => 'I think I found it but I am not quite sure.'
    }
  end
  
  it 'should have validations' do
    post = Post.new
    post.should_not be_valid
    post.title = @valid_attributes[:title]
    post.content = @valid_attributes[:content]
    post.author = @user
    p post
    post.should be_valid
  end

end

the_error

1)
NoMethodError in 'Post should have validations'
undefined method `new_record?' for #<Merb::Logger:0x274659c>
/Library/Ruby/Gems/1.8/gems/dm-core-0.9.7/lib/dm-core/property.rb:450:in `lazy_load'
/Library/Ruby/Gems/1.8/gems/dm-core-0.9.7/lib/dm-core/property.rb:390:in `get'
/Library/Ruby/Gems/1.8/gems/dm-core-0.9.7/lib/dm-core/property_set.rb:82:in `get'
/Library/Ruby/Gems/1.8/gems/merb-core-1.0.3/lib/merb-core/controller/mixins/render.rb:125:in `map'
/Library/Ruby/Gems/1.8/gems/dm-core-0.9.7/lib/dm-core/property_set.rb:55:in `each'
/Library/Ruby/Gems/1.8/gems/dm-core-0.9.7/lib/dm-core/property_set.rb:55:in `each'
/Library/Ruby/Gems/1.8/gems/dm-core-0.9.7/lib/dm-core/property_set.rb:82:in `map'
/Library/Ruby/Gems/1.8/gems/dm-core-0.9.7/lib/dm-core/property_set.rb:82:in `get'
/Library/Ruby/Gems/1.8/gems/dm-core-0.9.7/lib/dm-core/associations/relationship.rb:178:in `attach_parent'
/Library/Ruby/Gems/1.8/gems/dm-core-0.9.7/lib/dm-core/associations/many_to_one.rb:55:in `replace'
/Library/Ruby/Gems/1.8/gems/dm-core-0.9.7/lib/dm-core/associations/many_to_one.rb:21:in `author='
./spec/models/post_spec.rb:18: