Question

I have an Order model, which has_many payments and a checkout Controller. The Controller should create a new payment if no payment exits.

private 
# Helper method allows calling from several controller-callbacks.
def add_payment_if_not_exists
  if @order.payments.empty?
    Payment.create(...)
  end
end

And now I want to spec this behaviour in CheckoutControllerSpec

it 'should not add a payment when already added' do
  @order = mock_model(Order)
  @order.payments << mock_model(Payment).as_null_object

  Payment.should_not_receive(:new)
  post :homecoming, @params
end

But this throws

Failure/Error: @order.payments << mock_model(Payment).as_null_object
   Mock "Order_1003" received unexpected message :payments with (no args)

Somehow I still do not grok rspecs stubbing and mocking concept entirely. What am I aoing wrong?

Answer 1

@order = mock_model(Order)

Here you create a mock object, just a blank canvas. If you want to set stuff, you should tell it to respond to :payments with something. In this case, an array with 1 entry (a mock Payment object)

@order.stub(:payments) { [mock_model(Payment).as_null_object]}

That will get you further down the road. Other notes:

• I’m not sure that this expectation Payment.should_not_receive(:new) tests your behavior. You actually call Payment.create, not Payment.new
• I expect that you are stubbing out Order.find somewhere to return @order, but that’s not shown here, right?
• I would normally simplify your @order to the following:

Here we say that #payments returns a non-empty array, and we don’t care about the contents.

@order = mock_model(Order)
@order.stub(:payments) { [stub] }