Abstract: Miniaturization of Integrated Circuits (ICs) makes physical access for test purpose either difficult or even impossible. Further, the ICs growth along with its increasing complexity encounters the problem of large amount of test data also, number of access ports remains constant hence forcing towards long test application time. High speed ICs further complicates the testing problem enforces the high demand on tester’s driver/sensor mechanism and more complicated failure mechanism. This study discusses all such problem of the testing along with the test goal destination; Built In Self Test (BIST)-a final solution.