Resolve transactions with the tracking number!

app/models/transaction_resolver.rb

@@ -0,0 +1,10 @@
+class TransactionResolver
+  include Virtus.model
+
+  attribute :remaining_items, Array[Item]
+  attribute :fulfillment, Fulfillment
+
+  def items
+    self.remaining_items.select { |item| item.tracking_number == fulfillment.tracking_number }
+  end
+end

config/environment.rb

@@ -8,6 +8,7 @@
 require_relative '../app/models/item'
 require_relative '../app/models/order'
 require_relative '../app/models/order_loader'
+require_relative '../app/models/transaction_resolver'
 
 # Huh? https://github.com/RubyMoney/money/issues/593
 I18n.enforce_available_locales = false

spec/models/transaction_resolver_spec.rb

@@ -0,0 +1,38 @@
+require 'environment_helper'
+
+describe TransactionResolver do
+  context 'simplest case' do
+    let(:fulfillment) { Fulfillment.new(shipment_date: '11/01/16', total_price: '$12.34') }
+    let(:items) { [item] }
+    let(:item) { Item.new(title: 'Furby!', total_price: '$12.34') }
+
+    it 'correctly matches the shipments to the items memo' do
+      result = TransactionResolver.new(fulfillment: fulfillment, remaining_items: items).items
+      expect(result).to eq([item])
+    end
+  end
+
+  context 'one fulfillment, three items' do
+    let(:fulfillment) { Fulfillment.new(shipment_date: '11/05/16', total_price: '$3.00', tracking_number: 'AMZN_US(TBA109359633000)')}
+    let(:items) { [item_one, item_two, item_three] }
+    let(:item_one) { Item.new(title: 'Pickles!', total_price: '$1.50', tracking_number: 'AMZN_US(TBA109359633000)') }
+    let(:item_two) { Item.new(title: 'Pancakes!', total_price: '$1.50', tracking_number: 'AMZN_US(TBA109359633000)') }
+    let(:item_three) { Item.new(title: 'Dickle!', total_price: '$5.00', tracking_number: 'AMZN_US(BUTTS)') }
+
+
+    it 'correctly matches the shipments to the items memo' do
+      result = TransactionResolver.new(fulfillment: fulfillment, remaining_items: items).items
+      expect(result).to eq([item_one, item_two])
+    end
+  end
+
+  context 'when there is no match' do
+    let(:fulfillment) { Fulfillment.new(shipment_date: '11/05/16', total_price: '$3.00', tracking_number: 'AMZN_US(TBA109359633000)')}
+
+    it 'returns an empty array' do
+
+      result = TransactionResolver.new(fulfillment: fulfillment, remaining_items: []).items
+      expect(result).to be_empty
+    end
+  end
+end