Implement DefaultTax calculator compute method

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

@@ -4,29 +4,38 @@ def self.description
       I18n.t(:default_tax)
     end
 
-    def compute(order)
-      #rate = self.calculable
-      #tax = 0
-
-      #if rate.tax_category.is_default
-        #order.adjustments.each do |adjust|
-          #next if adjust.originator_type == 'Spree::TaxRate'
-          #next if adjust.originator_type == 'Spree::ShippingMethod' and not Spree::Config[:shipment_inc_vat]
-
-          #tax += (adjust.amount * rate.amount).round(2, BigDecimal::ROUND_HALF_UP)
-        #end
-      #end
-
-      #order.line_items.each do  | line_item|
-        #if line_item.product.tax_category  #only apply this calculator to products assigned this rates category
-          #next unless line_item.product.tax_category == rate.tax_category
-        #else
-          #next unless rate.tax_category.is_default # and apply to products with no category, if this is the default rate
-        #end
-        #tax += (line_item.price * rate.amount).round(2, BigDecimal::ROUND_HALF_UP) * line_item.quantity
-      #end
-
-      #tax
+    def compute(computable)
+      case computable
+        when Spree::Order
+          compute_order(computable)
+        when Spree::LineItem
+          compute_line_item(computable)
+      end
     end
+
+
+    private
+
+      def rate
+        rate = self.calculable
+      end
+
+      def compute_order(order)
+        matched_line_items = order.line_items.select do |line_item|
+          line_item.product.tax_category == rate.tax_category
+        end
+
+        line_items_total = matched_line_items.sum(&:price)
+        line_items_total + line_items_total * rate.amount
+      end
+
+      def compute_line_item(line_item)
+        if line_item.product.tax_category == rate.tax_category
+          line_item.price + line_item.price * rate.amount
+        else
+          0
+        end
+      end
+
   end
 end

core/spec/models/calculator/default_tax_spec.rb

@@ -1,38 +1,65 @@
 require 'spec_helper'
 
 describe Spree::Calculator::DefaultTax do
-  before do
-    #@tax_category = Factory(:tax_category, :tax_rates => [])
-    #@rate = mock_model(:tax_rate)
-    #@calculator = Spree::Calculator::DefaultTax.new(:calculable => @rate)
-  end
+  let!(:tax_category) { Factory(:tax_category, :tax_rates => []) }
+  let!(:rate) { mock_model(Spree::TaxRate, :tax_category => tax_category, :amount => 0.05) }
+  let!(:calculator) { Spree::Calculator::DefaultTax.new(:calculable => rate) }
+  let!(:order) { Factory(:order) }
+  let!(:product_1) { Factory(:product) }
+  let!(:product_2) { Factory(:product) }
+  let!(:line_item_1) { stub_model(Spree::LineItem, :product => product_1, :price => 10) }
+  let!(:line_item_2) { stub_model(Spree::LineItem, :product => product_2, :price => 5) }
 
   context "#compute" do
     context "when given an order" do
-      before { @order = Factory(:order) }
+      before do
+        order.stub :line_items => [line_item_1, line_item_2]
+      end
 
       context "when no line items match the tax category" do
-        #before do
-          #@order.stub :line_items => [Factory(:line_item), Factory(:line_item)]
-        #end
+        before do
+          product_1.tax_category = nil
+          product_2.tax_category = nil
+        end
 
-        pending "should be 0" do
-          @calculator.compute(@order).should == 0
+        it "should be 0" do
+          calculator.compute(order).should == 0
         end
       end
+
       context "when one item matches the tax category" do
-        pending "should be equal to the item total * rate"
+        before do
+          product_1.tax_category = tax_category
+          product_2.tax_category = nil
+        end
+
+        it "should be equal to the item total * rate" do
+          calculator.compute(order).should == 10.5
+        end
       end
+
       context "when more than one item matches the tax category" do
-        pending "should be equal to the sum of the item totals * rate"
+        it "should be equal to the sum of the item totals * rate" do
+          calculator.compute(order).should == 15.75
+        end
       end
     end
+
     context "when given a line item" do
       context "when the variant matches the tax category" do
-        pending "should be equal to the item total * rate"
+        it "should be equal to the item total * rate" do
+          calculator.compute(line_item_1).should == 10.5
+        end
       end
+
       context "when the variant does not match the tax category" do
-        pending "should be 0"
+        before do
+          line_item_2.product.tax_category = nil
+        end
+
+        it "should be 0" do
+          calculator.compute(line_item_2).should == 0
+        end
       end
     end
   end