软件测试作业二——分析bug并举例

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.

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

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

 

 

• • Identify the fault.

第一个：在递减的过程中没有遍历到0便结束循环导致循环不完整

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

应改正为

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

第二个：遇到符合条件的直接结束函数，不考虑之后的内容了，即返回第一个0，不返回最后一个0

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

应改正为

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

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

第一个：（不让它执行到该语句）test: x=[], y=1
第二个：（同样不让它执行到该语句）test:x=[]

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

第一个：test: x=[3,4,5], y=4 结果正确，并且也执行了fault
第二个：test: x=[1,0,1], Expected: 1

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

第一个：test: x=[3,4,5], y=2, 返回-1
第二个：test: x=[1,2,3], Expected: -1

转载于:https://www.cnblogs.com/brainchen/p/8549815.html