Code coverage
Beginner
A count of how much of the design’s written description the tests have actually used.
Novice
Coverage measured automatically from the design’s code: which lines ran, which way each if-statement went, which signals switched between 0 and 1, and which states of each state machine were visited.
Expert
Line, branch, condition, toggle, and FSM state and transition coverage. It measures activation only: a line holding a bug counts as covered even if the wrong value never reaches a checker. Required for sign-off, never sufficient on its own.