*************软件测试基础*************
首先解释一下fault、error以及failure的各自定义:
Fault:
可能导致系统或功能失效的异常条件(Abnormal condition that can cause an element or an item to fail.),可译为“故障”。
Error:
计算、观察或测量值或条件,与真实、规定或理论上正确的值或条件之间的差异(Discrepancy between a computed, observed or measured value or condition and the true, specified, or theoretically correct value or condition.),可译为“错误”。Error是能够导致系统出现Failure的系统内部状态。
Failure:
当一个系统不能执行所要求的功能时,即为Failure,可译为“失效”。(Termination of the ability of an element or an item to perform a function as required.)
Below are four faulty programs. Each includes a test case that results in failure. Answer the following questions 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
1. Identify the fault.
for循环中的条件判断应为:(int i=x.length-1; i > =0;i–);
2. If possible, identify a test case that does not execute the fault. (Reachability)
test: x=[];
(抛出空指针异常,没有执行下面的程序,则没有执行fault)
3. If possible, identify a test case that executes the fault, but does not result in an error state.
test: x=[3, 2, 5]; y = 2
Expected= 1
(执行了含有fault的程序,但是并没有产生错误,即执行了fault,没有执行error)
4. If possible identify a test case that results in an error, but not a failure.
test: x=[3, 2, 5]; y = 1 Expected = -1
(没有遍历x=1,直接返回了-1,因此执行了error,没有执行failure。)
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