Spec and refactor for pubsubhubbub/unsubscribe service (#2946)

* Add coverage for pubsub unsubscribe service

* Refactor pubsub unsubscribe service

app/services/pubsubhubbub/unsubscribe_service.rb

 # frozen_string_literal: true
 
 class Pubsubhubbub::UnsubscribeService < BaseService
-  def call(account, callback)
-    return ['Invalid topic URL', 422] if account.nil?
+  attr_reader :account, :callback_url
 
-    subscription = Subscription.find_by(account: account, callback_url: callback)
+  def call(account, callback_url)
+    @account = account
+    @callback_url = callback_url
 
-    unless subscription.nil?
-      Pubsubhubbub::ConfirmationWorker.perform_async(subscription.id, 'unsubscribe')
+    process_unsubscribe
+  end
+
+  private
+
+  def process_unsubscribe
+    if account.nil?
+      ['Invalid topic URL', 422]
+    else
+      confirm_unsubscribe unless subscription.nil?
+      ['', 202]
     end
+  end
+
+  def confirm_unsubscribe
+    Pubsubhubbub::ConfirmationWorker.perform_async(subscription.id, 'unsubscribe')
+  end
 
-    ['', 202]
+  def subscription
+    @_subscription ||= Subscription.find_by(account: account, callback_url: callback_url)
   end
 end

spec/services/pubsubhubbub/unsubscribe_service_spec.rb

+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe Pubsubhubbub::UnsubscribeService do
+  describe '#call' do
+    subject { described_class.new }
+
+    context 'with a nil account' do
+      it 'returns an invalid topic status' do
+        result = subject.call(nil, 'callback.host')
+
+        expect(result).to eq invalid_topic_status
+      end
+    end
+
+    context 'with a valid account' do
+      let(:account) { Fabricate(:account) }
+
+      it 'returns a valid topic status and does not run confirm when no subscription' do
+        allow(Pubsubhubbub::ConfirmationWorker).to receive(:perform_async).and_return(nil)
+        result = subject.call(account, 'callback.host')
+
+        expect(result).to eq valid_topic_status
+        expect(Pubsubhubbub::ConfirmationWorker).not_to have_received(:perform_async)
+      end
+
+      it 'returns a valid topic status and does run confirm when there is a subscription' do
+        subscription = Fabricate(:subscription, account: account, callback_url: 'callback.host')
+        allow(Pubsubhubbub::ConfirmationWorker).to receive(:perform_async).and_return(nil)
+        result = subject.call(account, 'callback.host')
+
+        expect(result).to eq valid_topic_status
+        expect(Pubsubhubbub::ConfirmationWorker).to have_received(:perform_async).with(subscription.id, 'unsubscribe')
+      end
+    end
+
+    def invalid_topic_status
+      ['Invalid topic URL', 422]
+    end
+
+    def valid_topic_status
+      ['', 202]
+    end
+  end
+end