rspec and ActiveRecord::Base.transaction testing

model.rb

def set_new_name_on_items?
  success = ActiveRecord::Base.transaction do
    model.items.each do |i|
      i.name = 'new name'
      i.save or raise ActiveRecord::Rollback
    end
  !!success
end

model_spec.rb

it 'returns false on a single failing transaction' do
  items = [ item_a, item_b ]
  model = Fabricate(:model, items: items)
  item_b.stub(:save!).and_return(false)
  
  expect(model.set_new_name_on_items).to be false
end

it 'returns true on all save transaction' do
  items = [ item_a, item_b ]
  model = Fabricate(:model, items: items)

  expect(model.set_new_name_on_items).to be true
end

actually, best way to stub this is: .stub(:create_or_update):
From the docs:

# File activerecord/lib/active_record/base.rb, line 2575
      def save
        create_or_update
      end

# File activerecord/lib/active_record/base.rb, line 2592
      def save!
        create_or_update || raise(RecordNotSaved)
      end

so, save and save! are slightly different but both call create_or_update.