Refactor domain expiration email

#186

spec/mailers/domain_mailer_spec.rb

@@ -0,0 +1,38 @@
+require 'rails_helper'
+
+RSpec.describe DomainMailer do
+  describe '#expiration' do
+    let(:domain) { instance_spy(Domain,
+                                name: 'test.com',
+                                registrant_email: 'registrant@test.com',
+                                admin_contact_emails: ['admin.contact.email@test.com']
+    ) }
+    let(:domain_presenter) { instance_spy(DomainPresenter) }
+    let(:registrar_presenter) { instance_spy(RegistrarPresenter) }
+    subject(:message) { described_class.expiration(domain: domain) }
+
+    before :example do
+      expect(DomainPresenter).to receive(:new).and_return(domain_presenter)
+      expect(RegistrarPresenter).to receive(:new).and_return(registrar_presenter)
+    end
+
+    it 'has valid sender' do
+      message.deliver!
+      expect(message.from).to eq(['noreply@internet.ee'])
+    end
+
+    it 'has registrant and administrative contacts as recipient' do
+      message.deliver!
+      expect(message.to).to match_array(['registrant@test.com', 'admin.contact.email@test.com'])
+    end
+
+    it 'has valid subject' do
+      message.deliver!
+      expect(message.subject).to eq('The test.com domain has expired')
+    end
+
+    it 'sends message' do
+      expect { message.deliver! }.to change { ActionMailer::Base.deliveries.count }.by(1)
+    end
+  end
+end