A simulation-after-test algorithm for the analog fault diagnosis problem is presented, in which a bound on the maximum number of simultaneous faults is used to minimize the number of test points required. Based on this self-testing algorithm, an analog automatic test program generation (AATPG) for both linear and nonlinear circuits and systems is being developed. The AATPG code is subdivided into off-line and on-line processes. The actual test can be run in either a fully automatic mode or interactively. In addition, the issues of parallel processing and testability for analog circuits and systems are also addressed.