软件测试作业——二

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.

a)
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
for (int i=x.length-1; i > 0; i--)
{
if (x[i] == y)
{
return i;
}
}
return -1;
}
// test: x=[2, 3, 5]; y = 2
// Expected = 0
b)
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
for (int i = 0; i < x.length; i++)
{
if (x[i] == 0)
{
return i;
}
} return -1;
}
// test: x=[0, 1, 0]
// Expected = 2

1.Identify the fault.

    a)i>0 should be i>=0

    b)for (int i = 0; i < x.length; i++)should be for(int i = x.length - 1; i >= 0; i --)

2.If possible, identify a test case that does not execute the fault. (Reachability).
    a) x=[2] y = 2;

    b) all input will execute the fault.

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

    a)x = [2,3,4] y = 3

    b)x=[0]

4.If possible identify a test case that results in an error, but not a failure.
    a) x=[2,3,4] y=5

    b) x = [3,0,8]