Flesh out Calculator behaviour

This adds the functionality to the calculator required to map per line
item taxes coming from the TaxJar API to the taxes required for each
line item in an order.

The calculator does not yet support shipping taxes.

1 files changed, 81 insertions, 8 deletions

diff --git a/spec/super_good/solidus_taxjar/tax_calculator_spec.rb b/spec/super_good/solidus_taxjar/tax_calculator_spec.rb
index eaf810c..02140da 100644
--- a/spec/super_good/solidus_taxjar/tax_calculator_spec.rb
+++ b/spec/super_good/solidus_taxjar/tax_calculator_spec.rb
@@ -1,21 +1,94 @@
 require 'spec_helper'
 
-RSpec.describe SuperGood::SolidusTaxJar::TaxCalculator do
+RSpec.describe ::SuperGood::SolidusTaxJar::TaxCalculator do
   describe "#calculate" do
     subject { calculator.calculate }
 
-    let(:calculator) { described_class.new(order) }
+    let(:calculator) { described_class.new(order, api: dummy_api) }
+
+    let(:dummy_api) do
+      instance_double ::SuperGood::SolidusTaxJar::API
+    end
 
     let(:order) do
-      Spree::Order.new(
-        id: 10
+      ::Spree::Order.new(
+        id: 10,
+        store: store,
+        ship_address: address
+      )
+    end
+
+    let(:store) do
+      ::Spree::Store.new(
+        name: "Default Store",
+        url: "https://store.example.com",
+        code: "store",
+        mail_from_address: "contact@example.com",
+        cart_tax_country_iso: "US"
       )
     end
 
-    it "returns the taxes" do
-      expect(subject.order_id).to eq order.id
-      expect(subject.line_item_taxes).to be_empty
-      expect(subject.shipment_taxes).to be_empty
+    context "when the order has an empty tax address" do
+      let(:address) { nil }
+
+      it "returns no taxes" do
+        expect(subject.order_id).to eq order.id
+        expect(subject.shipment_taxes).to be_empty
+        expect(subject.line_item_taxes).to be_empty
+      end
+    end
+
+    context "when the order has a non-empty tax address" do
+      let(:address) { ::Spree::Address.new(first_name: "Ronnie James") }
+
+      before do
+        allow(dummy_api).to receive(:tax_for).with(order).and_return(
+          instance_double(::Taxjar::Tax, breakdown: breakdown)
+        )
+      end
+
+      context "and there is a breakdown" do
+        let!(:tax_rate) do
+          ::Spree::TaxRate.create!(
+            name: "Sales Tax",
+            amount: 0.5,
+            calculator: ::Spree::Calculator.new
+          )
+        end
+
+        let(:breakdown) do
+          instance_double ::Taxjar::Breakdown, line_items: [taxjar_line_item]
+        end
+
+        let(:taxjar_line_item) do
+          instance_double ::Taxjar::BreakdownLineItem, id: "33", tax_collectable: 6.66
+        end
+
+        it "returns the taxes" do
+          expect(subject.order_id).to eq order.id
+          expect(subject.shipment_taxes).to be_empty
+          expect(subject.line_item_taxes.length).to eq 1
+
+          item_tax = subject.line_item_taxes.first
+          aggregate_failures do
+            expect(item_tax.item_id).to eq 33
+            expect(item_tax.label).to eq "Sales Tax"
+            expect(item_tax.tax_rate).to eq tax_rate
+            expect(item_tax.amount).to eq 6.66
+            expect(item_tax.included_in_price).to eq false
+          end
+        end
+      end
+
+      context "and there is not a breakdown" do
+        let(:breakdown) { nil }
+
+        it "returns no taxes" do
+          expect(subject.order_id).to eq order.id
+          expect(subject.shipment_taxes).to be_empty
+          expect(subject.line_item_taxes).to be_empty
+        end
+      end
     end
   end
 end