软件测试作业二

1.

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

answer:

1)  Fault：

for循环中的i>0使循环时取不到x[0]的值

2) Not execute the fault.

test: x = NULL, y=2

 

3) Executes the fault, but does not result in an error state.

test:x=[1,2,3];y=3

 

4)Results in an error, but not a failure.

 

test：x=[1,2,3],y=4

 

 

2.
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

 

 

 

answer:

 

1)  Fault：

 

 

for循环会导致返回的是第一个等于0的下标

2) Not execute the fault.

 

test: x = NULL

 

 

3) Executes the fault, but does not result in an error state.

 

 

test:x=[0,1,2]

 

 

4)Results in an error, but not a failure.

 

 

test:x=[2,0,3]