The purpose of Stripe test mode is to ensure that you get your code into a perfectly working state, and that each type of transaction you are dealing with is fully covered. You can even validate that WebHooks are working by pointing them at your application’s test API endpoints.
There’s not really a way of ‘testing’ inside of the live environment as such – typical practice would be to make a real transaction using a company credit card, or one that you are in control of. You can then logon to Stripe Admin and refund the payment once it succeeds.
This is the same with most payment gateways, although there are some that have test mode built into the live API, and used via a specific header, parameter or tracking identifier. Although, this is really just the same end result – you are still testing in test mode.