描述
It has been known for some time that, in a typical programming project, approximately 50% of the elapsed time and over 50% of the total cost are expended in testing the program or system being developed. Given that knowledge, one would expect that program testing would have by now been refined into an “exact science” , but this is far from tha actual case. In fact, less seems to be known about software testing than about any other aspect of software development. Furthermore, testing has been an “out-of-vogue（不流行的）” subject, meaning that there is a sparcity（稀少）of literature on the topic.
