Why doesn't validate_acceptance_of break my functional tests?

Question

Using Ruby on Rails 4.2.0.rc2 I added an 'Accept terms of service' checkbox to user registration

In the user model I added

attr_accessor :terms_of_service
validates_acceptance_of :terms_of_service, acceptance: true

In the view

<%= f.check_box :terms_of_service %>

and finally in the controller I added it to the list of parameters

def user_params
  params.require(:user).permit(:name, :email, :password, :password_confirmation, :terms_of_service)
end

This works as expected but since I made a change to the implementation I expected the related tests to be in the red. However, this test passes and I don't understand why:

assert_difference 'User.count', 1 do
   post users_path, user: { name:  "Example User",
                            email: "[email protected]",
                            password:              "password",
                            password_confirmation: "password" }
   end

I can re-write my tests like so

  test "accept terms of service" do
    get signup_path
    assert_no_difference 'User.count' do
        post users_path, user: { name:  "Example User",
                                 email: "[email protected]",
                                 password:              "password",
                                 password_confirmation: "password",
                                 terms_of_service: "0" }
    end

    assert_difference 'User.count', 1 do
        post users_path, user: { name:  "Example User",
                                 email: "[email protected]",
                                 password:              "password",
                                 password_confirmation: "password",
                                 terms_of_service: "1" }
    end
  end

but I am curious as to why the original test fails to fail. What I've taken away from this is that validates_acceptance_of passes for nil.

Is this the intended behaviour?

Answer 1

In a nutshell, yes, nil is allowed. I've had the same issue before.

active_model/validations/acceptance.rb

module ActiveModel
  module Validations
    class AcceptanceValidator < EachValidator # :nodoc:
      def initialize(options)
        super({ allow_nil: true, accept: "1" }.merge!(options))
        setup!(options[:class])
      end
      # ...
    end
    # ...
  end
  # ...
end

In the initializer, it merges allow_nil with the options, so yes, nil (or the lack of a value, I should say) is allowed for that. They mention it in the Rails Guide for acceptance, but I missed it.

This bit me a few times in my tests also - I kept getting passing validations when I was certain they should not pass. Now we know why!