软件测试 fault error和failure

一、

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、检测不到x[0]，7行大于号应该改为等于。

2、x = NULL

3、x = [1, 2, 3], y = 3

4、x = [1, 2, 3], y = 1

二、

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、只能返回第一个0的位置，未必是最后一个。

2、x = NULL

3、x = [1, 0]

4、x = [0, 1]