rspect transactional fixture problem

I am having a problem with the following test and I cannot figure out why. I am working through the tutorial on http://ruby.railstutorial.org/ and just finished chapter 9. It seems the following spec test works once and then in order to get it to pass again I have to purge the test database. This doesn't seem necessary if I have transactional fixtures enabled (which I do).

Here is the test:

       describe "success" do          it "should make a new user" do            lambda do              visit signup_path              fill_in "Name", :with => "Example User"              fill_in "Email", :with => "user@example.com"              fill_in "Password", :with => "foobar"              fill_in "Confirmation", :with => "foobar"              click_button              response.should have_selector("div.flash.success", :content => "Welcome")              response.should render_template('users/show')            end.should change(User, :count).by(1)          end        end