It’s a way to try out a font for free. Testing font licenses are for a fully functional version of the complete font family. The word “testing” is in the file name, and usage is restricted.
AM I PERMITTED TO SHARE DRAFTS MADE WITH TESTING FONTS?
You can share files with members of the design and approval team (your supervisor, the client) during the testing process. They must be informed of the testing font restrictions.
WHAT CAN’T I DO WITH TESTING FONTS?
The primary limitation is that testing fonts are not permitted to be used in any manner that is seen outside of the design and approval team. You can’t publish or publicize materials containing the fonts in any way, including via static imagery or in “teaser” posts. This includes internal announcements or communications.