The process area that addresses the definition of test functions and the establishment of test career paths is the Test Organization process area, found at TMMi Level 3. This process area focuses on creating a well-structured test organisation, defining various test functions, and establishing career paths for testers. Specific practices include defining roles for test specialists, assigning staff to those roles, and establishing career development frameworks to support the professional growth of testers within the organisation.
Reference:
"TMMi Level 3 Test Organization SG 2 specifically focuses on establishing test functions and test career paths".