Testers are Members of your Site who are capable of receiving any test messages that you may want to deploy before launching an actual mailing. When you click on the "Test/Schedule/Send" icon on the Unsent Mailings screen you will be taken to the Schedule Mailings page where you have the option to select test recipients from a list of Testers for the Site.
The Testers are created on the Testers screen of the Settings section. From here you can add new Testers or delete existing Testers. To add a new Tester, enter his or her e-mail address in the input box and click the "Add" button. If the Tester you have specified is already a Member of the Site, he or she will be added to the list of available Testers, and will appear as an option on the test recipient list when you send a test mailing.
Note: Every Tester must be a Member of the Site. This is because many mailings contain personalized information, such as a greeting which incorporates the Member's first name (e.g. "Dear ##FirstName##,"). If a Tester were not a Member of the Site, he or she would not have the appropriate profile information to generate the personalized message. Therefore, if you attempt to add a Tester who is not already a Member of the Site, you will receive a warning message and that individual will not be added as a Tester. To add the individual as a Tester, first go to the Add New Member screen in the Members section of Enterprise and create a new Member.