Testing strong parameters with shoulda_matchers - ruby-on-rails

Question

I'm having a hard time trying to figure out how to test the strong parameters with rspec and shoulda_matchers.
No matter what I've tried, I always get the message: RSpec::Expectations::ExpectationNotMetError: Expected POST #create to restrict parameters on :language_name to :name,
but it did not restrict any parameters.
This is my controller:
class LanguageNamesController < CrudController
inherit_resources
actions :all, :except => [:show]
private
def language_name_params
params.require(:language_name).permit(:name)
end
end
This is the test:
require 'rails_helper'
RSpec.describe LanguageNamesController, type: :controller do
describe "parameters" do
it do
lm_params = {
language_name: {
name: 'John'
}
}
expect(subject).to permit(:name).for(:create, params: { params: lm_params }).on(:language_name)
end
end
end
Also, I've tried this and got the same result:
it do
subject.params = ActionController::Parameters.new(language_name: {foo: 'bar', name: 'baz'})
expect(subject).to permit(:name).for(:create).on(:language_name)
end
if I try like this, I got ArgumentError: unknown keyword: language_name:
it do
lm_params = {
language_name: {
name: 'John'
}
}
expect(subject).to permit(:name).for(:create, params: lm_params).on(:language_name)
end
I'm using:
ruby 2.5.1
rails 5.1.6
shoulda-matchers 3.1.2
Anyone know how to solve this?
Thank you!
This is my workaround to test it:
it do
faker_name = Faker::Name.name
params = {
language_name: {name: faker_name, other_attribute: "other value"},
extra: {extra: 1}
}
get :index, params: params
expect(subject.send(:language_name_params)).to eq({"name"=> faker_name})
end

Answer 1

You do not need to create lm_params. Shoulda matchers are going to mock up the params object for you.
If you only need to test the permissions you can do should permit(:name).for(:create)
If you need to check for a value on a permitted parameter: should permit(:name).for(:create, params: {name: 'John'})
There are good examples in the documentation for strong_parameters_matcher.rb
EDIT: Another good source of documentation is the rubydoc for shoulda matchers.