Why does my test credit card fail on my published plan, and why does the plan show my integration's name?

Whether a test card works depends on which Stripe integration is selected as the default. In your Stripe integration settings, one connection is checked as default. If the live connection is the default, it rejects test card numbers. You cannot override the default on the payment form, so check which connection is the default.

Plans are created in your Stripe account. If you have both a test mode connection and a live account, a plan can exist on both, and with several payment integrations connected you see several options in the publish drop-down. The text shown next to Published on a plan is the name of the payment integration it was published with. A common tip is to add the word test to the end of the test integration's name, which is why it can appear on the plan label.