for G Suite / for Office 365
How can I use "Run in Test Mode" function?
When selecting "Run in Test Mode" on the filtering configuration screen by inserting a check mark, emails that match the filter will be "sent directly". The intention behind using this function is "to check on sent history if the rule condition can be detected". Due to this, we are currently recommending customers to create rules as test user if you want to prioritize the existing rules (encrypted/ suspended).
Regarding how to create a test user, please refer to the following article.