According to Section 2.1.2, a distinction should be made between a synchronous circuit and an asynchronous circuit. The difference, as far as testing is concerned, is first presented (Section 7.1). Then synchronous sequential circuits are considered in the main part of the chapter; however, the methods presented could be adapted to asynchronous circuits.

A sequential fault may be analysed using a Markov chain model, as already stated in Section 5.3. The detection process is studied in more detail in this chapter, particularly the behavior for a long test sequence (Section 7.2). Then approximate methods are presented in Section 7.3.

Although this book concentrates on testing digital circuits, the exact and approximate methods presented in this chapter may be applied to other systems which are modeled by finite state machines, particularly certain types of program and communication protocols.