Why do I get rendering logging in my Rails request tests?

Question

We got output like this running our request tests:

Running specs.
Started GET "/" for 127.0.0.1 at 2013-09-10 16:51:02 +0200
Processing by WelcomeController#index as HTML
  Rendered welcome/index.html.slim within layouts/application (57.9ms)
Completed 200 OK in 92ms (Views: 91.6ms | ActiveRecord: 0.0ms)

How do we get rid of that?

Answer 1

After a heroic debugging session by a co-worker, it turned out to be due to gem "rails_12factor" in the Gemfile, as encouraged by Heroku.

You want something like gem "rails_12factor", group: :production so it's not included in the test environment.

I've written to Heroku to update their docs to mention this.