acts_as_list_test.rb

def test_delete_middle
  assert_equal [1, 2, 3, 4], ListMixin.find(:all, :conditions => 'parent_id = 5', :order => 'pos').map(&:id)

  ListMixin.find(2).destroy

  assert_equal [1, 3, 4], ListMixin.find(:all, :conditions => 'parent_id = 5', :order => 'pos').map(&:id)

  assert_equal 1, ListMixin.find(1).pos
  assert_equal 2, ListMixin.find(3).pos
  assert_equal 3, ListMixin.find(4).pos

  ListMixin.find(1).destroy

  assert_equal [3, 4], ListMixin.find(:all, :conditions => 'parent_id = 5', :order => 'pos').map(&:id)

  assert_equal 1, ListMixin.find(3).pos
  assert_equal 2, ListMixin.find(4).pos
end