ruby on rails - Rspec test public controller method passing params to private controller method -

this controller:

class planscontroller    def use_new_card     @user = user.find_by_id(new_card_params[:user_id])     if new_stripe_card     ...   end    private    def new_card_params     params.permit(:user_id, :stripetoken)   end    def new_stripe_card     stripeservice.new({user_id: @user.id, customer_id: @user.stripe_customer_id, source: new_card_params[:stripetoken]}).new_card   end end 

i'm trying write controller spec tests when proper parameters post use_new_card method, new_stripe_card's stripeservice.new gets these parameters appropriately.

my spec looks far:

describe "when proper params passed"   before     @user = user.create(...)   end    "should allow stripeservice.new receive proper parameters"     stripeservice.should_receive(:new).with({user_id: @user.id, customer_id: @user.stripe_customer_id, source: "test"})     post :use_new_card, user_id: @user.id, stripetoken: "test"   end end 

but i'm getting

failure/error: post :use_new_card, user_id: @user.id, stripetoken: "test"  nomethoderror:    undefined method `new_card' nil:nilclass 

totally fair, i'm not sure how fix this... can't stub new_card because stubbed method on nil object still throw error (i tried adding stripeservice.any_instance.stub(:new_card).and_return(true) before block)

stubbed methods return nil default. use and_return specify value returned stub::

stripeservice.should_receive(:new).and_return(whatever) 

or using newer syntax

expect(stripeservice).to receive(:new).and_return(whatever) 

edit

pardon hand-waving. stub must return object act instance of stripeservice extent required purposes of test. example:

let(:new_card) { double } let(:new_stripe_service) { double(new_card: new_card) } ... expect(stripeservice).to receive(:new).and_return(new_stripe_service) 

now when test refers new_stripe_service, rspec return test double has method stub named #new_card, double. can add whatever additional stubs need make test pass. alternatively, can return actual instance of stripeservice new_stripe_service.