TotalOrderValue - handle changing discounts

I'm copying the algorithm from the Offer class to later remove the original one.

Author: andrzejkrzywda

rails_application/app/processes/processes/total_order_value.rb

@@ -5,7 +5,8 @@ class TotalOrderValue
     subscribes_to(
       Pricing::PriceItemAdded,
       Pricing::PriceItemRemoved,
-      Pricing::PercentageDiscountSet
+      Pricing::PercentageDiscountSet,
+      Pricing::PercentageDiscountChanged
     )
 
     private
@@ -27,6 +28,8 @@ def apply(event)
         state.with(lines:)
       when Pricing::PercentageDiscountSet
         state.with(discount_amount: event.data.fetch(:amount))
+      when Pricing::PercentageDiscountChanged
+        state.with(discount_amount: event.data.fetch(:amount))
       else
         state
       end

rails_application/test/processes/total_order_value_test.rb

@@ -124,6 +124,37 @@ def test_with_discount
       end
     end
 
+    def test_changed_discount
+      process = TotalOrderValue.new(event_store, command_bus)
+      product_id = SecureRandom.uuid
+      event_1 = price_item_added(product_id)
+      event_2 = Pricing::PercentageDiscountSet.new(data: {
+        order_id: order_id,
+        type: "test_discount",
+        amount: 10
+      })
+      event_3 = Pricing::PercentageDiscountChanged.new(data: {
+        order_id: order_id,
+        type: "test_discount",
+        amount: 20
+      })
+      event_store.append(event_1)
+      event_store.append(event_2)
+      event_store.append(event_3)
+      process.call(event_1)
+      process.call(event_2)
+      assert_events_contain(
+        "Processes::TotalOrderValue$#{event_3.data[:order_id]}",
+        Processes::TotalOrderValueUpdated.new(
+          data: {
+            total_value: 80,
+            order_id: order_id
+          }
+        )) do
+        process.call(event_3)
+      end
+    end
+
 
 
     private