test.rb

      names_in_old_order = sequence_with_activities.activities.map { |a| a.name }
      sequence_with_activities.activities[0].name.should == names_in_old_order[0]
      sequence_with_activities.activities[1].name.should == names_in_old_order[1]
      sequence_with_activities.activities[2].name.should == names_in_old_order[2]
      sequence_with_activities.lightweight_activities_sequences[0].update_attributes!(position: 1)
      sequence_with_activities.lightweight_activities_sequences[1].update_attributes!(position: 0)
      sequence_with_activities.lightweight_activities_sequences[2].update_attributes!(position: 2)
      sequence_with_activities.reload # sequence_with_activities.activities.reset
      names_in_new_order = sequence_with_activities.activities.map { |a| a.name }
      names_in_new_order[1].should == names_in_old_order[0]
      names_in_new_order[0].should == names_in_old_order[1]
      names_in_new_order[2].should == names_in_old_order[2]