Of all the developments of testable as well as reliable designs for computing systems, test generations for sequential circuits are usually viewed as one of the hard nuts to be solved in terms of complexity and time-consumption. Although some dozens of algorithms have been proposed to cope with these issues, much still remains to be desired in solving such problems so as to determine: (1) which of the existing test generation algorithms could be the most efficient for some particular circuits; (2) which parameters will have the most or least influences on test generations. For this purpose, a testability forecasting method for sequential circuits using regression models has been presented which a user usually needs for analyzing their own circuits and selecting the most suitable test generation algorithm from all possible algorithms available. Some examples and experimental results are also provided in order to show how helpful and practical the method is.