How to test your complete product setup?
Just set your product price to 0 and use E-junkie's ADD TO CART buttons to do a test purchase. Instead of going through your regular payment processor, you'll checkout using E-junkie's FREE CHECKOUT. If your product's are live on your site and you can't set the product price to 0, then you can create a discount code in E-junkie seller admin for a 100% discount for item total and shipping which you can then use to checkout for via FREE CHECKOUT.
For security, E-junkie does not allow using sandbox accounts. If you need to test your product setup complete with the real payment processor you are going to use, you will need purchase it yourself using a credit card that is not associated with your payment processor account where you are accepting payments. Of course most payment processors will let you refund the payment.
IMPORTANT NOTE: E-junkie cart needs to be tested online. So the page where you paste E-junkie cart buttons must be uploaded on a website for you to be able to test it correctly. Please note, E-junkie cart remembers the products added for 24 hours, so it's easy for you to get confused while testing (as you might add one product but another one might already be there). In this case, you can simply remove all products from the cart or to completely restart the shipping experience, just clear your browser cookies.