Abstract: There is provided method and apparatus for improving and making more effective the testing of very large scale integrated (VLSI) devices such as a synchronous random access memory (SDRAM), along with improving their performance and their yield in production. The method includes the steps of providing a VLSI device with switching circuitry which permits respective arrays or banks of the device to be tested alone or simultaneously with separate sequences of test mode signals to identify defects, interactions and unwanted limitations in the overall performance of the device; using the information thus obtained to modify the test mode signals and where indicated the design of the device; iterating the previous steps to optimize a test methodology for the device; and using the optimized test methodology during burn-in of production devices. Logic circuitry is added to a VLSI device to facilitate the improved testing capability.