I would advise against sending emails to these test contacts via your workflows as there's no guarantee these email addresses don't exist, and if even they don't exist you will get a lot of bounces which, if it happens a lot, could cause your Hubspot marketing email functionality to be suspended. Maybe just create yourself as a contact if you want to test sending email via a workflow.
Matthew Shepherd
Freelance HubSpot Consultant CRM Consultant | SEO Specialist