Ruby on Rails Background Jobs with Sidekiq

Testing Code for Idempotency

There’s no general way to test a piece of code to determine if it’s idempotent. It’s usually not possible to have all of your third-party service providers simulate error conditions, so testing idempotent code often involves testing that it behaves the way you intended, given the conditions you wrote it for.

The changes to send_notification_email were substantial. You added a new API call and complex logic to examine that call to figure out what to do. The example app doesn’t use mocking but since it does have the fake mail service running, you can use it to simulate the situation you’re checking for.

The core of the test will call send_notification_email, and will expect a previously-used email_id to be set ...