Software testing is an execution process of a program, aiming at finding and correcting errors in the tested software as much as possible and improving the reliability of the software. It is a very important and complicated work in the software life cycle, which is of great significance to the software reliability guarantee. At present, formal methods and program correctness proof technology are not expected to become practical methods, and software testing will remain an effective method to ensure software reliability for quite some time to come. The overall goal of software engineering is to make full use of limited human and material resources to complete software development projects with high efficiency and high quality. Insufficient testing is bound to make the software run with some hidden errors that have not been exposed, which will mean greater danger for users. Over-testing will waste a lot of valuable resources. By the end of the test, even if the error was found, it paid a high price.

A famous saying by p>E.W.Dijkstra illustrates this truth: "Program testing can only show the existence of errors, but not the absence of errors." It can be seen that the purpose of testing is to make the defects contained in the software lower than a certain value and maximize the ratio of output to input. I wonder if I can help you with the answer given by excellent employment.