add a cron job to send expiration notice

app/jobs/cron/send_api_token_expiration_notice_job.rb

@@ -0,0 +1,21 @@
+class Cron::SendAPITokenExpirationNoticeJob < Cron::CronJob
+  self.schedule_expression = "every day at midnight"
+
+  def perform
+    windows = [
+      1.day,
+      1.week,
+      1.month
+    ]
+
+    windows.each do |window|
+      APIToken
+        .with_expiration_notice_to_send_for(window)
+        .find_each do |token|
+        APITokenMailer.expiration(token).deliver_later
+        token.expiration_notices_sent_at << Time.zone.today
+        token.save!
+      end
+    end
+  end
+end

spec/jobs/cron/send_api_token_expiration_notice_job_spec.rb

@@ -0,0 +1,83 @@
+RSpec.describe Cron::SendAPITokenExpirationNoticeJob, type: :job do
+  describe 'perform' do
+    let(:administrateur) { create(:administrateur) }
+    let!(:token) { APIToken.generate(administrateur).first }
+    let(:mailer_double) { double('mailer', deliver_later: true) }
+    let(:today) { Date.new(2018, 01, 01) }
+
+    def perform_now
+      Cron::SendAPITokenExpirationNoticeJob.perform_now
+    end
+
+    before do
+      travel_to(today)
+      token.update!(created_at: today)
+      allow(APITokenMailer).to receive(:expiration).and_return(mailer_double)
+    end
+
+    context 'when the token does not expire' do
+      before { perform_now }
+
+      it { expect(mailer_double).not_to have_received(:deliver_later) }
+    end
+
+    context 'when the token expires in 6 months' do
+      let(:expires_at) { Date.new(2018, 06, 01) }
+      before do
+        token.update(expires_at:)
+        perform_now
+      end
+
+      it { expect(mailer_double).not_to have_received(:deliver_later) }
+
+      context 'when the token expires less than a month' do
+        before do
+          travel_to(expires_at - 1.month - 1.day)
+          perform_now
+
+          travel_to(expires_at - 1.month)
+          perform_now
+
+          travel_to(expires_at - 1.month + 1.day)
+          perform_now
+        end
+
+        it do
+          expect(mailer_double).to have_received(:deliver_later).once
+          expect(token.reload.expiration_notices_sent_at).to match_array([expires_at - 1.month])
+        end
+      end
+
+      context 'when the token expires less than a week' do
+        before do
+          travel_to(expires_at - 1.week)
+          2.times.each { perform_now }
+        end
+
+        it { expect(mailer_double).to have_received(:deliver_later).once }
+      end
+
+      context 'when we simulate the whole sequence' do
+        before do
+          travel_to(expires_at - 1.month)
+          2.times.each { perform_now }
+
+          travel_to(expires_at - 1.week)
+          2.times.each { perform_now }
+
+          travel_to(expires_at - 1.day)
+          2.times.each { perform_now }
+        end
+
+        it do
+          expect(mailer_double).to have_received(:deliver_later).exactly(3).times
+          expect(token.reload.expiration_notices_sent_at).to match_array([
+            expires_at - 1.month,
+            expires_at - 1.week,
+            expires_at - 1.day
+          ])
+        end
+      end
+    end
+  end
+end