gistfile1.cs

namespace StupidExample {

   public class CustomerGateway {
        IUnitOfWorkManager work;

        public CustomerGateway(IUnitOfWorkManager work) { this.work = work; }

        public IEnumerable<Customer> GetNewCustomersSince(DateTime time) {
            work.On("CustomerDB", session => 
                session.CreateCriteria<Customer>()
                       .Add(Expression.Gt("EffectiveDate", time))
                       .List<Customer>());

   }

   public class when_there_are_new_customers : with_the_customer_database {
      Establish context = () => {
         work = MockRepository.GenerateStub<IUnitOfWorkManager>();
         work.Stub(x => x.On("CustomerDB", Arg.Is.Anything))
             .Return(null)
             .WhenCalled(invocation => invocation.ReturnValue 
                     = ((Func<ISession,IEnumerable<Customer>>) invocation.Arguments[1])(session));
                         
      }

      It notices_there_are_new_customers_and_starts_dealing_with_it = () => 
         gotNewCustomers.ShouldBeTrue();
   }

}