Add test for promotion duplication job

app/jobs/duplicate_promotion_job.rb

@@ -0,0 +1,14 @@
+class DuplicatePromotionJob
+  include Sidekiq::Job
+
+  def perform(params)
+    promotion = find_promotion(params[:promotion_id])
+    Spree::PromotionHandler::PromotionDuplicator.new(promotion).duplicate
+  end
+
+  private
+
+  def find_promotion(id)
+    Spree::Promotion.find(id)
+  end
+end

spec/jobs/duplicate_promotion_job_spec.rb

@@ -0,0 +1,32 @@
+require 'spec_helper'
+
+describe DuplicatePromotionJob do
+  describe "#perform" do
+    subject(:execute_job) { described_class.new.perform(params) }
+
+    let(:promotion) { build(:promotion) }
+
+    let(:params) do
+      { promotion_id: promotion.id }
+    end
+
+    let(:double) { instance_double(Spree::PromotionHandler::PromotionDuplicator) }
+
+    before do
+      allow(Spree::Promotion)
+        .to receive(:find)
+        .and_return(promotion)
+    end
+
+    it "sends #duplicate to the duplicator service" do
+      expect(Spree::PromotionHandler::PromotionDuplicator)
+        .to receive(:new)
+        .with(promotion)
+        .and_return(double)
+      expect(double)
+        .to receive(:duplicate)
+
+        execute_job
+    end
+  end
+end