Mocking successive return values

I’m having a problems mocking successive return values. I don’t know
if I’m doing something wrong or if this is a limitation of rspec
mocks. Any ideas of what I may be doing wrong?

I’m trying to test the generate_quote_number method. It generates a
quote number, looks to see if it is in the db already. If it is, it
calls itself to try again. I want to test that it looks in the
database for matching numbers until it finds one which does not exist
already.

The code

def generate_quote_number
quote_num = “MMQ#{self.random_string}-001”
if Policy.find(:first, :conditions => [“quote_number = ?”,
quote_num])
quote_num = generate_quote_number
end
quote_num
end

def random_string(size=8)
# return a random string
end

For the test, I simply lookup 3 existing quote numbers, append nil to
the end (for a total of 4)

The test

it “should not generate a duplicate quote number” do
existing_quote_numbers = Policy.find(:all).map{|p| p.quote_number}
[0,3]

@policy_service
.should_receive
(:random_string
).with
(:no_args
).exactly(4).times.and_return(existing_quote_numbers.concat([nil]))
@policy_service.generate_quote_number
end

The result

should not generate a duplicate quote number
Mock ‘Service::Base’ expected :random_string with (no args) 4 times,
but received it once

I verified “and_return” is actually returning the array rather than an
individual element of the existing_quote_numbers array which makes
sense, but what about this?
http://rspec.rubyforge.org/svn/branches/dogfood/spec/spec/mocks/mock_spec.rb

specify “should use a list of return values for successive calls” do

@mock.should_receive(:multi_call).twice.with(:no_args).and_return([8,
12])
@mock.multi_call.should_equal 8
@mock.multi_call.should_equal 12
@mock.__verify
end

Any feedback on how to properly test this is much appreciated.

Thanks,
Doug