Move the strange refunding logic from Spree::TaxRate into the default tax calculator

core/app/models/spree/calculator/default_tax.rb

@@ -18,7 +18,8 @@ def compute_order(order)
 
       line_items_total = matched_line_items.sum(&:discounted_amount)
       if rate.included_in_price
-        round_to_two_places(line_items_total - ( line_items_total / (1 + rate.amount) ) )
+        order_tax_amount = round_to_two_places(line_items_total - ( line_items_total / (1 + rate.amount) ) )
+        refund_if_necessary(order_tax_amount, order.tax_zone)
       else
         round_to_two_places(line_items_total * rate.amount)
       end
@@ -49,7 +50,22 @@ def round_to_two_places(amount)
 
     def deduced_total_by_rate(item, rate)
       unrounded_net_amount = item.discounted_amount / (1 + sum_of_included_tax_rates(item))
-      round_to_two_places(unrounded_net_amount * rate.amount)
+      refund_if_necessary(
+        round_to_two_places(unrounded_net_amount * rate.amount),
+        item.order.tax_zone
+      )
+    end
+
+    def refund_if_necessary(amount, order_tax_zone)
+      if default_zone_or_zone_match?(order_tax_zone)
+        amount
+      else
+        amount * -1
+      end
+    end
+
+    def default_zone_or_zone_match?(order_tax_zone)
+      Zone.default_tax.try!(:contains?, order_tax_zone) || rate.zone.contains?(order_tax_zone)
     end
   end
 end

core/app/models/spree/tax_rate.rb

@@ -104,20 +104,11 @@ def adjust(order_tax_zone, item)
 
     # This method is used by Adjustment#update to recalculate the cost.
     def compute_amount(item)
-      if included_in_price && !default_zone_or_zone_match?(item.order.tax_zone)
-        # In this case, it's a refund.
-        calculator.compute(item) * - 1
-      else
-        calculator.compute(item)
-      end
+      calculator.compute(item)
     end
 
     private
 
-    def default_zone_or_zone_match?(order_tax_zone)
-      Zone.default_tax.try!(:contains?, order_tax_zone) || zone.contains?(order_tax_zone)
-    end
-
     def adjustment_label(amount)
       Spree.t translation_key(amount),
               scope: "adjustment_labels.tax_rates",

core/spec/models/spree/calculator/default_tax_spec.rb

@@ -1,51 +1,55 @@
 require 'spec_helper'
 
 describe Spree::Calculator::DefaultTax, type: :model do
-  let!(:address) { create(:address) }
-  let!(:zone) { create(:zone, name: "Country Zone", default_tax: true, countries: [address.country]) }
-  let!(:tax_category) { create(:tax_category) }
+  let(:address) { create(:address) }
+  let!(:zone) { create(:zone, name: "Country Zone", default_tax: true, countries: [tax_rate_country]) }
+  let(:tax_rate_country) { address.country }
+  let(:tax_category) { create(:tax_category) }
   let!(:rate) { create(:tax_rate, tax_category: tax_category, amount: 0.05, included_in_price: included_in_price, zone: zone) }
   let(:included_in_price) { false }
-  let!(:calculator) { Spree::Calculator::DefaultTax.new(calculable: rate ) }
-  let!(:order) { create(:order, ship_address: address) }
-  let!(:line_item) { create(:line_item, price: 10, quantity: 3, tax_category: tax_category) }
-  let!(:shipment) { create(:shipment, cost: 15) }
+  subject(:calculator) { Spree::Calculator::DefaultTax.new(calculable: rate ) }
 
   context "#compute" do
     context "when given an order" do
-      let!(:line_item_1) { line_item }
-      let!(:line_item_2) { create(:line_item, price: 10, quantity: 3, tax_category: tax_category) }
+      let(:order) do
+        create(
+          :order_with_line_items,
+          line_items_attributes: [
+            { price: 10, quantity: 3, tax_category: tax_category }.merge(line_item_one_options),
+            { price: 10, quantity: 3, tax_category: tax_category }.merge(line_item_two_options)
+          ],
+          ship_address: address
+        )
+      end
+      let(:line_item_one_options) { {} }
+      let(:line_item_two_options) { {} }
 
-      before do
-        allow(order).to receive_messages line_items: [line_item_1, line_item_2]
+      context "when all items matches the rate's tax category" do
+        it "should be equal to the sum of the item totals * rate" do
+          expect(calculator.compute(order)).to eq(3)
+        end
       end
 
       context "when no line items match the tax category" do
-        before do
-          line_item_1.tax_category = nil
-          line_item_2.tax_category = nil
-        end
+        let(:other_tax_category) { create(:tax_category) }
+        let(:line_item_one_options) { { tax_category: other_tax_category } }
+        let(:line_item_two_options) { { tax_category: other_tax_category } }
 
         it "should be 0" do
           expect(calculator.compute(order)).to eq(0)
         end
       end
 
       context "when one item matches the tax category" do
-        before do
-          line_item_1.tax_category = tax_category
-          line_item_2.tax_category = nil
-        end
+        let(:other_tax_category) { create(:tax_category) }
+        let(:line_item_two_options) { { tax_category: other_tax_category } }
 
         it "should be equal to the item total * rate" do
           expect(calculator.compute(order)).to eq(1.5)
         end
 
         context "correctly rounds to within two decimal places" do
-          before do
-            line_item_1.price = 10.333
-            line_item_1.quantity = 1
-          end
+          let(:line_item_one_options) { { price: 10.333, quantity: 1 } }
 
           specify do
             # Amount is 0.51665, which will be rounded to...
@@ -54,12 +58,6 @@
         end
       end
 
-      context "when more than one item matches the tax category" do
-        it "should be equal to the sum of the item totals * rate" do
-          expect(calculator.compute(order)).to eq(3)
-        end
-      end
-
       context "when tax is included in price" do
         let(:included_in_price) { true }
 
@@ -70,54 +68,149 @@
           # 60 - 57.14 = $2.86
           expect(calculator.compute(order).to_f).to eql 2.86
         end
+
+        context "when the order's tax address is outside the default VAT zone" do
+          let(:order_zone) { create(:zone, countries: [address.country]) }
+          let(:default_vat_country) { create(:country, iso: "DE") }
+
+          before do
+            rate.zone.update(countries: [default_vat_country])
+            # The order has to be reloaded here because of tax zone caching.
+            order.reload
+          end
+
+          it 'creates a negative amount, indicating a VAT refund' do
+            expect(subject.compute(order)).to eq(-2.86)
+          end
+        end
       end
     end
+  end
+
+  shared_examples_for 'computing any item' do
+    let(:promo_total) { 0 }
+    let(:order) { build_stubbed(:order, ship_address: address) }
 
     context "when tax is included in price" do
       let(:included_in_price) { true }
+
       context "when the variant matches the tax category" do
+        it "should be equal to the item's full price * rate" do
+          expect(calculator.compute(item)).to eql 1.43
+        end
+
         context "when line item is discounted" do
-          before do
-            line_item.promo_total = -1
-          end
+          let(:promo_total) { -1 }
 
           it "should be equal to the item's discounted total * rate" do
-            expect(calculator.compute(line_item)).to eql 1.38
+            expect(calculator.compute(item)).to eql 1.38
           end
         end
 
-        it "should be equal to the item's full price * rate" do
-          expect(calculator.compute(line_item)).to eql 1.43
+        context "when the order's tax address is outside the default VAT zone" do
+          let!(:order_zone) { create(:zone, countries: [address.country]) }
+          let(:default_vat_country) { create(:country, iso: "DE") }
+
+          before do
+            rate.zone.update(countries: [default_vat_country])
+          end
+
+          it 'creates a negative amount, indicating a VAT refund' do
+            expect(subject.compute(item)).to eq(-1.43)
+          end
         end
       end
     end
 
     context "when tax is not included in price" do
       context "when the line item is discounted" do
-        before { line_item.promo_total = -1 }
+        let(:promo_total) { -1 }
 
         it "should be equal to the item's pre-tax total * rate" do
-          expect(calculator.compute(line_item)).to eq(1.45)
+          expect(calculator.compute(item)).to eq(1.45)
         end
       end
 
       context "when the variant matches the tax category" do
         it "should be equal to the item pre-tax total * rate" do
-          expect(calculator.compute(line_item)).to eq(1.50)
+          expect(calculator.compute(item)).to eq(1.50)
         end
       end
     end
+  end
 
-    context "when given a shipment" do
-      it "should be 5% of 15" do
-        expect(calculator.compute(shipment)).to eq(0.75)
-      end
+  describe 'when given a line item' do
+    let(:item) do
+      build_stubbed(
+        :line_item,
+        price: 10,
+        quantity: 3,
+        promo_total: promo_total,
+        order: order,
+        tax_category: tax_category
+      )
+    end
 
-      it "takes discounts into consideration" do
-        shipment.promo_total = -1
-        # 5% of 14
-        expect(calculator.compute(shipment)).to eq(0.7)
-      end
+    it_behaves_like 'computing any item'
+  end
+
+  describe 'when given a shipment' do
+    let(:shipping_method) do
+      build_stubbed(
+        :shipping_method,
+        tax_category: tax_category
+      )
     end
+
+    let(:shipping_rate) do
+      build_stubbed(
+        :shipping_rate,
+        selected: true,
+        shipping_method: shipping_method
+      )
+    end
+
+    let(:item) do
+      build_stubbed(
+        :shipment,
+        cost: 30,
+        promo_total: promo_total,
+        order: order,
+        shipping_rates: [shipping_rate]
+      )
+    end
+
+    it_behaves_like 'computing any item'
+  end
+
+  describe 'when given a shipping rate' do
+    let(:shipping_method) do
+      build_stubbed(
+        :shipping_method,
+        tax_category: tax_category
+      )
+    end
+
+    let(:shipment) do
+      build_stubbed(
+        :shipment,
+        order: order
+      )
+    end
+
+    let(:item) do
+      # cost and discounted_amount for shipping rates are the same as they
+      # can not be discounted. for the sake of passing tests, the cost is
+      # adjusted here.
+      build_stubbed(
+        :shipping_rate,
+        cost: 30 + promo_total,
+        selected: true,
+        shipping_method: shipping_method,
+        shipment: shipment
+      )
+    end
+
+    it_behaves_like 'computing any item'
   end
 end