软件测试作业2 — 样例测试

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

Questions：
1、Identify the fault.

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

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

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

 

Answer：

Program1:

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

1.Fault：

　　Line 6：i > 0 

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

2. A test case that does not execute the fault:

　　x=[ ];  y =2 

　　Expected: NullPointerException   

　　Actual: NullPointerException

3. A test case that executes the fault, but does not result in an error state:

　　x=[2,3,5]; y=3

　　Expected: 1

　　Actual: 1

4. A test case that results in an error, but not a failure:

　　x=[2,3,5];  y=4    

　　Expected:-1   

　　Actual: -1

 

Program2:

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.Fault：

　　Line 5：for (int i = 0; i < x.length; i++) 

　　　　it should be if(int i = x.length-1; i>=0; i--)

2. A test case that does not execute the fault:

　　x=[ ];

　　Expected: NullPointerException   

　　Actual: NullPointerException

3. A test case that executes the fault, but does not result in an error state:

　　x=[1,1,1];

　　Expected: -1

　　Actual: -1

4. A test case that results in an error, but not a failure:

　　x=[1,0,1]; 

　　Expected:2   

　　Actual: 2