Wix app billing test payment

I have created a Wix app using the Wix CLI. I want to accept payments from site owners after they install my app on their site. I have created two plans on the Pricing page of my app dashboard:

  1. Base plan ($10, one-time payment)

  2. Pro plan ($20, one-time payment).

Since these plans are not recurring, I decided to use an external payment page. From this external page, I am calling the Wix Checkout API (https://www.wixapis.com/apps/v1/checkout) using the OAuth API (https://www.wixapis.com/oauth2/token).

The checkout URL is generated successfully, but after redirecting to the checkout page, I am unable to test the payment using a test card. It shows the following error:

“Your card was declined. Your request was in live mode, but used a known test card.”

How can I test the payment flow in the development environment using test cards?