Enhances ActionMailer to support the :cache delivery method, which behaves like :test, except that the deliveries are marshalled to a temporary cache file, thus making them available to other processes.

Our test raises an ActiveRecord::RecordNotFound exception. We know that Rails has special handling to return a 404 status code in this case. However, the request spec still raises the exception.

GitLab is transitioning from controller specs to request specs.

There is no request.env in functional tests because the functional tests are supposed to remain at the controller level.

Run the complete unit with a certain input set, and test the side-effects. This differs to the Rails Way™ testing style, where smaller units of code, such as a specific validation or a callback, are tested in complete isolation. While that might look tempting and clean, it will create a test environment that is not identical to what happens in production.