class A
          include Mongoid::Document
          include Mongoid::Timestamps::Short

          embeds_many :bs, cascade_callbacks: true

          accepts_nested_attributes_for :bs 

          field :name
        end

        class B
          include Mongoid::Document
          include Mongoid::Timestamps::Short

          embeds_many :cs, cascade_callbacks: true

          accepts_nested_attributes_for :cs 

          field :name
        end

        class C
          include Mongoid::Document
          include Mongoid::Timestamps::Short

          field :name
        end

        it 'push multiple' do
          a = A.create(name: "A Name")
          b = a.bs.create(name: "B Name")

          a.bs_attributes = { 
            "0" => {
              "cs_attributes" => {
                "0" => {
                  "name" => "C Name"
                }
              },
              "id" => b.id.to_s
            },
            "1" => {
              "name" => "New B Name"
            }
          }

          expect(a.atomic_updates).to eq({
            "$push" => {"bs.0.cs"=>{"$each"=>[{"_id"=>b.cs.first.id, "name"=>"C Name"}]}},
            :conflicts => {"$push"=>{"bs"=>{"$each"=>[{"_id"=>a.bs.last.id, "name"=>"New B Name"}]}}}
          })

          a.send(:prepare_update, {}) do
             expect(a.atomic_updates).to eq({})
          end