Why doesn't validate_acceptance_of break my functional tests? - ruby-on-rails

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: "user#example.com",
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: "user#example.com",
password: "password",
password_confirmation: "password",
terms_of_service: "0" }
end
assert_difference 'User.count', 1 do
post users_path, user: { name: "Example User",
email: "user#example.com",
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!