Add Make ActionMailer Synchronous In Test as a rails til

rails/make-action-mailer-synchronous-in-test.md

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+# Make ActionMailer Synchronous In Test
+
+When you set up an `ActionMailer` email, the default configuration is for it
+to use `ActiveJob` to send the emails. [As of Rails 5, it will do so
+asynchronously.](https://blog.bigbinary.com/2016/03/29/rails-5-changed-default-active-job-adapter-to-async.html).
+Depending on your preferences for testing emails, you may prefer `ActiveJob`
+to send the emails synchronously. This can be done by changing the
+`queue_adapter` back to `:inline` in your `config/environments/test.rb`.
+
+```ruby
+config.active_job.queue_adapter = :inline
+```
+
+If you also configure the `delivery_method` as `:test`:
+
+```ruby
+config.action_mailer.delivery_method = :test
+```
+
+then emails will be queued up in `ActionMailer::Base.deliveries` allowing
+you to write a test like this:
+
+```ruby
+expect(ActionMailer::Base.deliveries.count).to eq(1)
+```
+
+Check out [the
+docs](https://guides.rubyonrails.org/action_mailer_basics.html) for more on
+`ActionMailer`.
+
+[source](https://stackoverflow.com/a/42987726/535590)