Problem

When you are adding new attributes to your model after the initial creation, they are not by default included in the permitted parameters list. Sometimes the error is not so obvious to see when testing, unless you look at the test log files.

Solution

To make the error more obvious, there is the following configuration option that you can set up in config/environments/test.rb (tip taken from Rails 4 In Action):

config.action_controller.action_on_unpermitted_parameters = :raise