shows some unexpected (to me) behavior of DataMapper

count_test.rb

require 'dm-core'
require 'dm-migrations'
require 'dm-aggregates'
require 'test/unit'

class Animal
  include DataMapper::Resource

  property :id, Serial

  def self.small
    all(:id.lte => 2)
  end

end


DataMapper::Logger.new("/tmp/dmtestlog", :debug)
DataMapper.setup(:default, 'sqlite:///tmp/testdb')
DataMapper.auto_migrate!!
DataMapper.finalize

5.times do
  Animal.create
end

class CountTest < Test::Unit::TestCase

  def test_total_count
    assert_equal 5, Animal.count
  end
  
  def test_slice_count
    a = Animal.all(:id.lte => 5)
    b = Animal.all(:id.lte => 4)
    assert_equal 1, (a-b).count, "The difference leaves one item"
    assert_equal 1, (a-b).small.count, "Adding a the small filter should not make the count larger"  
  end

end