Zakeke allows you to test your customizable product and generate test print-ready files to make sure all is good before publishing the product live to your store.
Go to Customizable Products and click on Preview on the product you wish to test. You find your test orders in Orders > Test.
See the video tutorial below.
PLEASE NOTE: this is only available for the Visual Product Customizer solution. Also, you won't be able to test the following tool in the testing customizer (they work only on the real customizer at your website):