问题描述：
Below are four faulty programs Each includes a test case that results in
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
