RSpec Mock Object Example

Question

I am new to mock objects, and I am trying to learn how to use them in RSpec. Can someone please post an example (a hello RSpec Mock object world type example), or a link (or any

Answer 1

Current (3.x) RSpec provides both pure mock objects (as in tokhi's answer) and partial mocking (mocking calls to an existing object). Here's an example of partial mocking. It uses expect and receive to mock an Order's call to a CreditCardService, so that the test passes only if the call is made without having to actually make it.

class Order
  def cancel
     CreditCardService.instance.refund transaction_id
  end
end

describe Order do
  describe '#cancel' do
    it "refunds the money" do
      order = Order.new
      order.transaction_id = "transaction_id"
      expect(CreditCardService.instance).to receive(:refund).with("transaction_id")
      order.cancel
    end
  end
end

In this example the mock is on the return value of CreditCardService.instance, which is presumably a singleton.

with is optional; without it, any call to refund would satisfy the expectation. A return value could be given with and_return; in this example it is not used, so the call returns nil.

---

This example uses RSpec's current (expect .to receive) mocking syntax, which works with any object. The accepted answer uses the old rspec-rails mock_model method, which was specific to ActiveModel models and was moved out of rspec-rails to another gem.