No checkout cart in Magento

Hi there,
I'm using your awesome tool with the ecommerce shop software Magento 1.
For the first run I'm using a vanilla installation.

When I use the clickselector to add a product to the cart I can see in the reference screenshot that there is a new product added to the cart. Great!
But when I now add a new scenario and make a screenshot of the cart the screenshot says that the cart is empty.
Is BackstopJS using a unique browser session for each screenshot?
Otherwise I can't understand the problem. If the current user/guest is adding a product to the cart and the browser session is still the same then I can see my product when I go to the cart url.