Gemfile

dm_version = '=0.10.3'
gem 'dm-core',               dm_version, :git => 'git://github.com/datamapper/dm-core'
gem "data_objects",          '=0.10'
gem "do_sqlite3",            '=0.10'

only :test do
  gem 'rspec', :require_as => 'spec'
end

stives.rb

require 'vendor/gems/environment'
Bundler.require_env
DataMapper.setup(:default, 'sqlite3:///tmp/stives.db')

class Man
  include DataMapper::Resource
  property :id, Serial
  property :name, String

  has n, :wives    # n should probably be 7, but oh well...
  has n, :sacks, :through => :wives
  has n, :cats, :through => :sacks
  # kits aren't really needed to illustrate these bugs;
  # we apologize to all the nursery-rhyme purists
end

class Wife
  include DataMapper::Resource
  property :id, Serial
  property :name, String
  belongs_to :man
  has n, :sacks
end

class Sack
  include DataMapper::Resource
  property :id, Serial
  belongs_to :wife
  has n, :cats
end

class Cat
  include DataMapper::Resource
  property :id, Serial
  property :name, String
  belongs_to :sack
end

# DataObjects::Sqlite3.logger = DataObjects::Logger.new(STDOUT, 0)

describe "chained many-to-one relationships" do
  def create_man
    man = Man.create(
      :name => "Albert",
      :wives => [
        Wife.new(
          :name => "Brenda",
          :sacks => [
            Sack.new(
              :cats => [
                Cat.new(:name => 'Fluffy'),
                Cat.new(:name => 'Hairball'),
              ]),
            Sack.new(
              :cats => [
                Cat.new(:name => 'Underfoot'),
                Cat.new(:name => 'Death of Mice'),
              ])
          ]),
        Wife.new(
          :name => 'Carol',
          :sacks => [
            Sack.new(
              :cats => [
                Cat.new(:name => 'Felix'),
                Cat.new(:name => 'Tiger'),
              ]),
            Sack.new(
              :cats => [
                Cat.new(:name => 'Muffin'),
                Cat.new(:name => 'Princess')
              ])
          ]),
      ])
    raise "invalid test setup" if man.new?
    man
  end

  describe "finding objects" do
    before(:all) do
      DataMapper.auto_migrate!
      @man = create_man
    end

    it "finds things 1 layer deep" do
      @man.wives.size.should == 2
    end
    
    it "finds things 2 layers deep" do
      @man.sacks.size.should == 4
    end

    it "finds things 3 layers deep" do
      @man.cats.size.should == 8
    end
  end

  describe "destroying objects" do
    before(:each) do
      DataMapper.auto_migrate!
      @man = create_man
    end

    it "destroys only the specified things (simple many-to-one)" do
      lambda do
        lambda do
          lambda do
            lambda do
              @man.wives.destroy!
            end.should_not change { Man.all.size }
          end  .should     change { Wife.all.size }.by(-2)
        end    .should_not change { Sack.all.size }
      end      .should_not change { Cat.all.size }
    end

    # fails: it deletes the sacks, but also the wives
    it "destroys only the specified things (two-level many-to-one)" do
      lambda do
        lambda do
          lambda do
            lambda do
              @man.sacks.destroy!
            end.should_not change { Man.all.size }
          end  .should_not change { Wife.all.size }
        end    .should     change { Sack.all.size }.by(-4)
      end      .should_not change { Cat.all.size }
    end

    # fail: it deletes the cats, but also the sacks and wives
    it "destroys only the specified things (three-level many-to-one)" do
      lambda do
        lambda do
          lambda do
            lambda do
              @man.cats.destroy!
            end.should_not change { Man.all.size }
          end  .should_not change { Wife.all.size }
        end    .should_not change { Sack.all.size }
      end      .should     change { Cat.all.size }.by(-8)
    end
  end
end