【正文】 sidered a successful program. Here’s a description of the program:The program reads three integer values from an input dialog. The three values represent the lengths of the sides of a triangle. The program displays a message that states whether the triangle is scalene, isosceles, or equilateral.Remember that a scalene triangle is one where no two sides are equal, whereas an isosceles triangle has two equal sides, and an equilateral triangle has three sides of equal length. Moreover, the angles opposite the equal sides in an isosceles triangle also are equal (it also follows that the sides opposite equal angles in a triangle are equal), and all angles in an equilateral triangle are equal.Evaluate your set of test cases by using it to answer the following questions. Give yourself one point for each “yes” answer.1. Do you have a test case that represents a valid scalene triangle? (Note that test cases such as 1,2,3 and 2,5,10 do not warrant a “yes” answer because there does not exist a triangle having these dimensions.)2. Do you have a test case that represents a valid equilateral triangle? 3. Do you have a test case that represents a valid isosceles triangle? (Note that a test case representing 2,2,4 would not count because it is not a valid triangle.)4. Do you have at least three test cases that represent valid isosceles triangles such that you have tried all three permutations of two equal sides (such as, 3,3,4。 3,4,3。 and 4,3,3)?5. Do you have a test case in which one side has a zero value? 2 The Art of Software Testing 6. Do you have a test case in which one side has a negative value? 7. Do you have a test case with three integers greater than zero such that the sum of two of the numbers is equal to the third? (That is, if the program said that 1,2,3 represents a scalene triangle, it would contain a bug.)8. Do you have at least three test cases in category 7 such that you have tried all three permutations where the length of one side is equal to the sum of the lengths of the other two sides (for example, 1,2,3。 1,3,2。 and 3,1,2)?9. Do you have a test case with three integers greater than zero such that the sum of two of the numbers is less than the third (such as 1,2,4 or 12,15,30)?10. Do you have at least three test cases in category 9 such that you have tried all three permutations (for example, 1,2,4。 1,4,2。 and 4,1,2)? 11. Do you have a test case in which all sides are zero (0,0,0)? 12. Do you have at least one test case specifying noninteger values (such as ,)? 13. Do you have at least one test case specifying the wrong number of values (two rather than three integers, for example)? 14. For each test case did you specify the expected output from the program in addition to the input values? Of course, a set of test cases that satisfies these conditions does not guarantee that all possible errors would be found, but since questions 1 through 13 represent errors that actually have occurred in different versions of this program, an adequate test of this program should expose at least these errors.Now, before you bee concerned about your own score, consider this: In our experience, highly qualified professional programmers score, on the average, only out of a possible 14. If you’ve done better, congratulations。 if not, we’ll try to help.The point of the exercise is to illustrate that the testing of even a trivial program such as this is not an easy task. And if this is true, consider the difficulty of testing a 100,000statement air traffic control A SelfAssessment Test 3 system, a piler, or even a mundane payroll program. Testing also bees more difficult with the objectoriented languages such as Java and C++. For example, your test cases for applications built with these languages must expose errors associated with object instantiation and memory management.It might seem, from working with this example, that thoroughly testing a plex, realworld program would be impossible. Not so! Although the task can be daunting, adequate program testing is a very necessary—and achievable—part of software development, as you will learn in this book.CHAPTER 2The Psychology andEconomics ofProgram TestingSoftware testing is a technical task, but it also involves some important considerations of economics and human psychology.In an ideal world, we would want to test every possible permutation of a program. In most cases, however, this simply is not a seemingly simple program can have hundreds or thousands of possible input and output binations. Creating test cases for all of these possibilities is impractical. Complete testing of a plex application would take too long and require too many human resources to be economically feasible.In addition, the software tester needs the proper attitude (perhaps “vision” is a better word) to successfully test a software some cases, the tester’s attitude may be more important than the actual process itself. Therefore, we will start our discussion of software testing with these issues before we delve into the more technical nature of the topic.THE PSYCHOLOGY OF TESTINGOne of the primary causes of poor program testing is the fact that most programmers begin with a false definition of the term. They might say: ? “Testing is the process of demonstrating that errors are not present.” 5 Or ? “The purpose of testing is to show that a program performs its intended functions correctly.” Or ? “Testing is the process of establishing confidence that a program does what it is supposed to do.”These definitions are upsidedown.When you test a program, you want to add some value to value through testing means raising the quality or reliability of the program. Raising the reliability of the program means finding and removing errors.Therefore, don’t test a program to show that it works。 rather, you should start with the assumption that the program contains errors (a valid assumption for almost any progr