Request: Using Test (Temporary) Credentials to Connect a Payment Provider

Feature Request|We are collecting votes for this issue
Certain payment providers offer test credentials which you can use while waiting for your account to be approved. Currently, we're unable to accept test credentials when connecting your site to one of the relevant providers. 
If you already set up your account using these credentials, disconnect from the provider and reconnect it using the live credentials.
We are always working to update and improve our products, and your feedback is hugely appreciated.