relevant https://tasdikrahman.me/2020/10/07/why-I-chose-to-do-tdd-for-my-side-project/

tdd-slide-snippet.diff

diff --git a/app/jobs/check_certificate_job.rb b/app/jobs/check_certificate_job.rb
index 93fb16b..76f995b 100644
+++ b/app/jobs/check_certificate_job.rb
--- a/app/jobs/check_certificate_job.rb
@@ -10,7 +10,7 @@ class CheckCertificateJob < ApplicationJob
     Domain.all.each do |domain|
       if domain.certificate_expiring?
         Rails.logger.info("#{domain.fqdn} is expiring within the buffer period")
+        if (Figaro.env.send_expiry_notifications_to_slack == 'true') && !Figaro.env.slack_webhook_url.empty?
-        if (Figaro.env.send_expiry_notifications_to_slack == true) && !Figaro.env.slack_webhook_url.empty?
           message = "Your #{domain.fqdn} is expiring at #{domain.certificate_expiring_not_before}, please renew your cert"
           slack_notifier = SlackNotifier.new(Figaro.env.slack_webhook_url)
           begin
diff --git a/spec/jobs/check_certificate_job_spec.rb b/spec/jobs/check_certificate_job_spec.rb
index f4fa49b..71c40c8 100644
+++ b/spec/jobs/check_certificate_job_spec.rb
--- a/spec/jobs/check_certificate_job_spec.rb
@@ -48,7 +48,7 @@ RSpec.describe CheckCertificateJob, type: :job do

           it 'will not call SlackNotifier#notify' do
             allow_any_instance_of(Domain).to receive(:certificate_expiring?).and_return(true)
+            allow(Figaro).to receive_message_chain(:env, :send_expiry_notifications_to_slack).and_return('false')
-            allow(Figaro).to receive_message_chain(:env, :send_expiry_notifications_to_slack).and_return(false)
             allow(Figaro).to receive_message_chain(:env, :slack_webhook_url).and_return(slack_webhook_url)
             expect_any_instance_of(SlackNotifier).not_to receive(:notify).with(anything)