If you are working locally, install something like Papercut SMTP that acts as a local SMTP server but ensures all your emails are sent to the application rather than real people. It allows you see what what is being sent and fully test email functionality.
Hope this helps.
For locally testing: what Robert says,
For testing this on your test-environment and other non-productive environments: create an environment-variable, set it to ‘P’ on the production-environment and another value on the other environments, in the email-microflow add a decision checking the environment-variable, if not ‘P’ replace Email/To to your testmail-adres.
Prevent accidentally setting it to ‘P’ on non-production or vice verse. Either can/will have unwanted results. So even better: download and install module ‘SystemManagement’ which already has such a environment-variable and also checks at startup, if that variable is set correctly.