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Be Careful that you don't Stub your Big Toe

Posted by Tue, 13 Feb 2007 07:09:00 GMT

In a project that I’m currently working on, we’re handling recurring payments for subscribers. I’ve decided to play with a different payment service API on this project (TrustCommerce), which supposedly has one of the easier systems to handle recurring payments as well as one-time charges to the same credit cards. They store all the credit card data so that our delivered product to the client is CISP-compliant.

I came across the TrustCommerce Subscription plugin for Rails, which does just everything that I need to do in this first product release… as well as things that aren’t requirements just yet.

Well, I got my test account from TrustCommerce and was working on some RSpecs to test my new subscription and noticed that it was failing. After some snooping around the error responses, I realized that… test accounts don’t give you the ability to test the Citadel features of TrustCommerce. It’ll be another week or so before finish getting our account setup, so what am I to do? I really want to finish writing these specs and move on to the other portions that are dependent upon this working.

Suppose that you were going to perform something like this in an AR callback.


class BillingDetail < ActiveRecord::Base

  # validations    

  before_create :store_credit_card_data_with_trust_commerce

  private 

    def store_credit_card_data_with_trust_commerce
      # some of this is still test data... prettyu much copied from the README
      # TODO: refactor... but keep me out of controllers!
      response = TrustCommerceGateway::Subscription.create(
          :cc =>  self.credit_card_number, 
          :exp => '0412', 
          :name => self.customer_name,
          :amount => 1,
          :cycle => '1y',
          :demo => 'y'
        )

      if response['status'] == 'approved'
          self.billing_id = response['billingid']
        else
        # handle failure
        end
    end
end

Enter Mock Objects

Since I am unable to succesfully use the TrustCommerceGateway::Subscription.create method until I get our real account, I needed a simple way to emulate the interaction with the web service.

This can be done by using a Mock object, which RSpec provides for you.


TrustCommerceGateway::Subscription.stub!(:create).and_return( {expected response} )

Let’s look at the following spec file (much of it removed to protect the innocent).


module ValidBillingDetail
  def valid_attributes
    { # a hash of valid key/values for this model }
  end

  def approved_trust_commerce_subscription
    { 'status' => 'approved', 'billingid' => '1093423' } 
  end
end

context "A new billing detail" do
  include ValidBillingDetail

  setup do
    TrustCommerceGateway::Subscription.stub!(:create).and_return( approved_trust_commerce_subscription )
  end

  # bunch of other specs

  specify "should store new billing info with 3rd party API and store the billingid" do
    @billing_detail = BillingDetail.create( valid_attributes )
    @billing_detail.billing_id.should_not_be nil
  end
end  

You’ll notice a few things. First, you’ll see that I’ve stubbed the create method and when it is called in the method in my model, it’ll return the hash that I’ve specified.

TrustCommerceGateway::Subscription.stub!(:create).and_return( approved_trust_commerce_subscription )

In the spec, you will see that I am checking that that the .billing_id.should_not_be nil. If you look back in the method in the model above, you will notice that an approved subscription returns a billing_id, which is set when the transaction is successful.

This is working out great for me and because the documentation is fairly easy to follow, I’m going to be able to mock much of the behavior that I’ll be using in the application, without needing to even connect to their API.

If you’re using RSpec, I highly encourage you to read more about mocks objects.

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