Extract out helper method. Additional specs

lib/payment_processor/go_cardless/helper.rb

@@ -0,0 +1,23 @@
+module PaymentProcessor
+  module GoCardless
+    module Helper
+      extend self
+
+      # Returns the next date for the passed day.
+      #
+      # === Attributes
+      #
+      # *day+ - The day to set the date too.
+      def next_available_date(day)
+        date = Date.today.change(day: day)
+
+        if Time.now.day >= day
+          date += 1.month
+        end
+
+        date
+      end
+    end
+  end
+end
+

lib/payment_processor/go_cardless/populator.rb

@@ -28,7 +28,7 @@ def subscription_params
             interval_unit: "monthly"
           }.tap do |params|
             if bacs?
-              params[:start_date] = subscription_start_date
+              params[:start_date] = Helper.next_available_date(Settings.gocardless.gbp_charge_day.to_i)
             end
           end
         )
@@ -77,18 +77,8 @@ def client
         )
       end
 
-      def subscription_start_date
-        date = Date.today.change(day:20)
-
-        if Time.now.day >= settings_charge_day
-          date += 1.month
-        end
-
-        date
-      end
-
       def charge_date
-        if Settings.gocardless.gbp_charge_day.blank? || mandate.scheme.downcase != 'bacs'
+        if Settings.gocardless.gbp_charge_day.blank? || !bacs?
           return mandate.next_possible_charge_date
         end
 

spec/lib/payment_processor/go_cardless/helper_spec.rb

@@ -0,0 +1,39 @@
+require 'rails_helper'
+
+describe PaymentProcessor::GoCardless::Helper do
+  describe '.next_available_date' do
+    subject { PaymentProcessor::GoCardless::Helper }
+
+    context 'day has not passed' do
+      it 'returns current month' do
+        Timecop.freeze('5 May') do
+          expect(subject.next_available_date(6)).to eq(Date.parse('6 May'))
+        end
+      end
+    end
+
+    context 'day is today' do
+      it 'returns with following month' do
+        Timecop.freeze('5 May') do
+          expect(subject.next_available_date(5)).to eq(Date.parse('5 June'))
+        end
+      end
+    end
+
+    context 'day has passed' do
+      it 'returns with following month' do
+        Timecop.freeze('5 May') do
+          expect(subject.next_available_date(4)).to eq(Date.parse('4 June'))
+        end
+      end
+    end
+
+    context 'invalid day' do
+      it 'raises argument error' do
+        expect {
+          subject.next_available_date(32)
+        }.to  raise_error(ArgumentError, 'invalid date')
+      end
+    end
+  end
+end

spec/lib/payment_processor/go_cardless/subscription_spec.rb

@@ -32,11 +32,13 @@ module GoCardless
             links: double(customer: 'CU00000', mandate: 'MA00000')
           )
         end
+
         let(:mandate) do
           instance_double('GoCardlessPro::Resources::Mandate',
             id: 'MA00000', scheme: 'sepa', next_possible_charge_date: 1.day.from_now
           )
         end
+
         let(:subscription) { instance_double('GoCardlessPro::Resources::Subscription', id: 'SU00000') }
 
         let(:amount_in_dollars){ 12.5 }
@@ -57,6 +59,28 @@ module GoCardless
 
         include_examples 'transaction and subscription', :make_subscription
 
+        describe 'charge date' do
+          subject { described_class.make_subscription(required_options) }
+
+          let(:mandate) do
+            instance_double('GoCardlessPro::Resources::Mandate',
+              id: 'MA00000',
+              scheme: 'bacs',
+              next_possible_charge_date: 1.day.from_now )
+          end
+
+          it 'sets start date for bacs' do
+            required_options
+            expect_any_instance_of(
+              GoCardlessPro::Services::SubscriptionsService
+            ).to receive(:create).with(
+              params: hash_including(start_date: instance_of(Date))
+            )
+
+            subject
+          end
+        end
+
         describe 'calling the GC SDK' do
           it 'creates a subscription with the right params' do
             expect_any_instance_of(

spec/requests/api/go_cardless/go_cardless_spec.rb

@@ -401,19 +401,15 @@
 
         shared_examples 'successful subscription' do
           it 'passes the correct data to the GoCardless Payment SDK' do
-
             sdk_params[:params] = sdk_params[:params].merge(
               name: "donation",
               interval_unit: "monthly",
-              start_date: Date.parse("2016/02/20")
+              start_date: instance_of(Date)
             )
             subscriptions_service = instance_double(GoCardlessPro::Services::SubscriptionsService, create: double(id: 'asdf'))
             allow_any_instance_of(GoCardlessPro::Client).to receive(:subscriptions).and_return(subscriptions_service)
             expect(subscriptions_service).to receive(:create).with(sdk_params)
-
-            Timecop.freeze('2016/01/21') do
-              subject
-            end
+            subject
           end
 
           it 'posts donation action to queue with correct data' do