Regression
Beginner
The big set of tests run again and again, usually every night, to catch anything a new change broke.
Novice
The full collection of tests, each run many times with different random seeds, rerun automatically (usually every night) to catch anything a new change broke. Results, coverage and failures are tracked over time.
Expert
Run by tooling that schedules thousands of jobs, groups failures by their first error message, merges coverage and ranks tests. Pass rate, new-failure count and coverage trend are the daily health metrics.