How do test email notifications work, and what must you set up?

Testers and test plan/package owners can get email when a test case runs — only the first error, or on completion.

You must register the user and assign a test-process role (Tester / Test plan responsible / Test package responsible — these are test attributes, unrelated to SAP roles), and set the SU01 parameter AGS_SMT_NOTIFICATION (a 4-char X-position string per role).