Sophia here from Shopify. An update to order and payment testing on development stores was posted on March 30, 2020 in the Developer changelog. This change was made to keep development stores in line with their intended purpose as a testing environment. You will still be able to process unlimited test transactions in development stores, and in cases where a real order needs to be placed, you can hand development stores over to clients, at which point they can select a paid plan. Please let me know if you have any questions.