Add order_shipping_method specs to cover select_shipping_method

app/models/concerns/order_shipping_method.rb

@@ -23,12 +23,13 @@ module OrderShippingMethod
   #
   # @return [Shipment]
   def select_shipping_method(shipping_method_id)
-    return if shipping_method_id.nil? || shipments.empty?
+    return if shipping_method_id.blank? || shipments.empty?
     shipment = shipments.first
 
     shipping_rate = shipment.shipping_rates.find_by_shipping_method_id(shipping_method_id)
     return unless shipping_rate
 
     shipment.selected_shipping_rate_id=(shipping_rate.id)
+    shipment.shipping_method
   end
 end

spec/models/concerns/order_shipping_method_spec.rb

@@ -3,15 +3,15 @@ require 'spec_helper'
 describe OrderShippingMethod do
   let(:order) { create(:order) }
 
-  describe '#shipping_method' do
-    context 'when order has no shipments' do
-      it 'returns nil' do
+  describe "#shipping_method" do
+    context "when order has no shipments" do
+      it "returns nil" do
         expect(order.shipping_method).to be_nil
       end
     end
 
-    context 'when order has single shipment' do
-      it 'returns the shipments shipping_method' do
+    context "when order has single shipment" do
+      it "returns the shipments shipping_method" do
         shipping_method = create(:shipping_method_with, :flat_rate)
         shipment = create(:shipment_with, :shipping_method, shipping_method: shipping_method)
         order.shipments = [shipment]
@@ -20,4 +20,61 @@ describe OrderShippingMethod do
       end
     end
   end
+
+  describe "#select_shipping_method" do
+    let(:shipping_method) { create(:shipping_method_with, :flat_rate) }
+
+    context "when order has no shipment" do
+      it "returns nil" do
+        expect(order.select_shipping_method(shipping_method.id)).to be_nil
+      end
+    end
+
+    context "when order has a shipment" do
+      let(:shipment) { create(:shipment_with, :shipping_method, shipping_method: shipping_method) }
+      before { order.shipments = [shipment] }
+
+      context "when no shipping_method_id is provided" do
+        it "returns nil for nil shipping_method_id" do
+          expect(order.select_shipping_method(nil)).to be_nil
+        end
+
+        it "returns nil for empty shipping_method_id" do
+          empty_shipping_method_id = ' '
+          expect(shipment.shipping_rates).to_not receive(:find_by_shipping_method_id).with(empty_shipping_method_id)
+
+          expect(order.select_shipping_method(empty_shipping_method_id)).to be_nil
+        end
+      end
+
+      context "when shipping_method_id is not valid for the order" do
+        it "returns nil" do
+          invalid_shipping_method_id = order.shipment.shipping_method.id + 1000
+          expect(shipment.shipping_rates).to receive(:find_by_shipping_method_id).with(invalid_shipping_method_id) { nil }
+
+          expect(order.select_shipping_method(invalid_shipping_method_id)).to be_nil
+        end
+      end
+
+      context "when shipping_method_id is valid for the order" do
+        it "returns the shipments shipping_method" do
+          expect(shipment).to receive(:selected_shipping_rate_id=)
+
+          expect(order.select_shipping_method(shipping_method.id)).to eq shipping_method
+        end
+      end
+
+      context "when multiple shipping_methods exist in the shipment" do
+        let(:expensive_shipping_method) { create(:shipping_method_with, :expensive_name) }
+        before { shipment.add_shipping_method(expensive_shipping_method, false ) }
+        it "selects a shipping method that was not selected by default" do
+          expect(shipment.shipping_method).to eq shipping_method
+
+          expect(order.select_shipping_method(expensive_shipping_method.id)).to eq expensive_shipping_method
+
+          expect(shipment.shipping_method).to eq expensive_shipping_method
+        end
+      end
+    end
+  end
 end