PODEM
Beginner
A faster way to search for a test pattern, by guessing only the chip’s inputs and checking each guess.
Novice
Path-Oriented Decision Making (Goel, 1981), a test-search method that only ever guesses values for the circuit’s inputs, simulates what follows, and undoes the latest guess when the fault can no longer be made visible.
Expert
The decision tree is over primary inputs, not all lines. Each objective is traced back to one input using controllability estimates, and a check that the fault effect can still reach an output prunes dead branches early. The basis of most later ATPG engines.