Active Merchant Integration

Hi

I am trying to integrate Active merchant in my rails project to implement
the Paypal recurring express checkout option for online payments.

I am trying to integration tests and am not being able to determine how to
mock the PaypalExpressResponse class. When I try this

@response = mock(ActiveMerchant::Billing::PaypalExpressResponse,
:token=>'fake_paypal_token')
RECURRING_GATEWAY.stub(:authorization).and_return(@response)

I get this error in when I run my tests

Mock ActiveMerchant::Billing::PaypalExpressResponse received unexpected
message :recycle! with (no args)

What am I doing wrong? I am quite new to rails and am not being able to find
much help anywhere. Any direction would be greatly appreciated.

Thank you!