Specs for pubsub subscribe service (#2951)

* Add spec for pubsubhubbub/subscribe

* Refactor pubsubhubbub/subscribe service

spec/services/pubsubhubbub/subscribe_service_spec.rb

@@ -0,0 +1,71 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe Pubsubhubbub::SubscribeService do
+  describe '#call' do
+    subject { described_class.new }
+    let(:user_account) { Fabricate(:account) }
+
+    context 'with a nil account' do
+      it 'returns the invalid topic status results' do
+        result = service_call(account: nil)
+
+        expect(result).to eq invalid_topic_status
+      end
+    end
+
+    context 'with an invalid callback url' do
+      it 'returns invalid callback status when callback is blank' do
+        result = service_call(callback: '')
+
+        expect(result).to eq invalid_callback_status
+      end
+      it 'returns invalid callback status when callback is not a URI' do
+        result = service_call(callback: 'invalid-hostname')
+
+        expect(result).to eq invalid_callback_status
+      end
+    end
+
+    context 'with a blocked domain in the callback' do
+      it 'returns callback not allowed' do
+        Fabricate(:domain_block, domain: 'test.host', severity: :suspend)
+        result = service_call(callback: 'https://test.host/api')
+
+        expect(result).to eq not_allowed_callback_status
+      end
+    end
+
+    context 'with a valid account and callback' do
+      it 'returns success status and confirms subscription' do
+        allow(Pubsubhubbub::ConfirmationWorker).to receive(:perform_async).and_return(nil)
+        subscription = Fabricate(:subscription, account: user_account)
+
+        result = service_call(callback: subscription.callback_url)
+        expect(result).to eq success_status
+        expect(Pubsubhubbub::ConfirmationWorker).to have_received(:perform_async).with(subscription.id, 'subscribe', 'asdf', 3600)
+      end
+    end
+  end
+
+  def service_call(account: user_account, callback: 'https://callback.host', secret: 'asdf', lease_seconds: 3600)
+    subject.call(account, callback, secret, lease_seconds)
+  end
+
+  def invalid_topic_status
+    ['Invalid topic URL', 422]
+  end
+
+  def invalid_callback_status
+    ['Invalid callback URL', 422]
+  end
+
+  def not_allowed_callback_status
+    ['Callback URL not allowed', 403]
+  end
+
+  def success_status
+    ['', 202]
+  end
+end