You can use the Test API key to test your payment methods and check the webhook on your website. To do this, you should use the Test API key instead of the Live API key when you connect Mollie to your website. You can change to the Live API key after you have finished making test transactions. Test transactions do not deduct any amount from your account, but you will be able to view these test payments in your Mollie Dashboard.
You can also check that the connection between Mollie and your website is working correctly. For example, when a payment is made, feedback is sent via this connection so that your system will know when to mark an order as Paid.
You can find more about setting up your payment methods, webhooks, integrations, point of sale solution etc in our article on Testing.