软件测试Homework02

软件测试Homework02

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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.

Identify the fault.

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

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

3) If possible, identify a test case that results in an error， but not a  failure

 

public int findTheLast (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;

}

Answer：

fault: 当x非空时，x[0]不会与y比较

 

1)   Test case : x = []; y = 2;  

 

2)   Test case : x = [0, 1, 2]; y = 1; i = 2, return 1

 

3)   Test case : x = [1, 2, 3]; y = 1; i = 2, return -1

  

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：

fault: 当数组中存在多个0时，上面的程序返回的时第一个0的位置

  

1)   Test case: x = [];

 

2)   Test case : x = [0, 1, 2];

 

3)   Test case : x = [0, 1, 0];