Memory BIST (MBIST)
Beginner
A tiny built-in tester next to each memory block. It writes values into every spot and reads them back to check.
Novice
Memory built-in self-test: a small test controller placed beside each on-chip memory. It writes and reads set patterns through every address at full speed and reports pass or fail, often with the failing addresses so the memory can be repaired.
Expert
Generated per memory instance: a controller, address and data generators and a comparator. Runs March-style algorithms, feeds repair with spare rows and columns, and is reached through JTAG or IJTAG.