软件测试作业（二）

问题描述：

Below are four faulty programs. Each includes a test case that results in failure. Answer the following questions (in the next slide) about each program.

问题1： Identify the fault. 

public int findLast (int[] x, int y) {
 //Effects: If x==null throw NullPointerException 
// else return the index of the last element 
// in x that equals y. 
// If no such element exists, return -1 
            int index = -1;
            for (int i=x.length-1; i >= 0; i--) 
            {
                         if (x[i] == y) 
                         { 
                              index = i; 
                         } 
            }

public static int lastZero (int[] x) {
//Effects: if x==null throw NullPointerException 
// else return the index of the LAST 0 in x.
// Return -1 if 0 does not occur in x 
              int index = -1;
              for (int i = 0; i < x.length; i++) 
              {
                     if (x[i] == 0) 
                    { 
                        index = i; 
                    } 
               } 
               return index; 
}
// test: x=[0, 1, 0] 
// Expected = 2

return index; } // test: x=[2, 3, 5]; y = 2 // Expected = 0

　　问题2： If possible, identify a test case that does not execute the fault. (Reachability) 

      2.1  case：x=[2,3,5]; y=3;

             expect = 1;

             result = 1;

      2.2  case: x=[0,1,1];

              expect = 0;

              result = 0;

      问题3： If possible, identify a test case that executes the fault, but does not result in an error state.

           impossible

      问题4：If possible identify a test case that results in an error, but not a failure.

           impossible