Add RSpec tests and shared contexts for monetizable attributes and currency detection

Author: RubenIgnacio

spec/active_record/monetizable/currency_for_spec.rb

@@ -0,0 +1,55 @@
+# encoding: utf-8
+
+require 'spec_helper'
+
+require_relative 'money_helpers'
+
+if defined? ActiveRecord
+  describe MoneyRails::ActiveRecord::Monetizable do
+    include MoneyHelpers
+
+    describe "#currency_for" do
+      context "when detecting currency based on different conditions" do
+        it "detects currency based on instance currency name" do
+          product = Product.new(sale_price_currency_code: 'CAD')
+          currency = product.send(:currency_for, :sale_price, :sale_price_currency_code, nil)
+
+          expect_to_be_a_currency_instance(currency)
+          expect_currency_iso_code(currency, 'CAD')
+        end
+
+        it "detects currency based on currency passed as a block" do
+          product = Product.new
+          currency = product.send(:currency_for, :lambda_price, nil, ->(_) { 'CAD' })
+
+          expect_to_be_a_currency_instance(currency)
+          expect_currency_iso_code(currency, 'CAD')
+        end
+
+        it "detects currency based on currency passed explicitly" do
+          product = Product.new
+          currency = product.send(:currency_for, :bonus, nil, 'CAD')
+
+          expect_to_be_a_currency_instance(currency)
+          expect_currency_iso_code(currency, 'CAD')
+        end
+      end
+
+      context "when falling back to a default or registered currency" do
+        it "falls back to a registered currency" do
+          product = Product.new
+          currency = product.send(:currency_for, :amount, nil, nil)
+
+          expect_equal_currency(currency, Product.currency)
+        end
+
+        it "falls back to a default currency" do
+          transaction = Transaction.new
+          currency = transaction.send(:currency_for, :amount, nil, nil)
+
+          expect_equal_currency(currency, Money.default_currency)
+        end
+      end
+    end
+  end
+end