*************軟體測試基礎*************
首先解釋一下fault、error以及failure的各自定義:
Fault:
可能導緻系統或功能失效的異常條件(Abnormal condition that can cause an element or an item to fail.),可譯為“故障”。
Error:
計算、觀察或測量值或條件,與真實、規定或理論上正确的值或條件之間的差異(Discrepancy between a computed, observed or measured value or condition and the true, specified, or theoretically correct value or condition.),可譯為“錯誤”。Error是能夠導緻系統出現Failure的系統内部狀态。
Failure:
當一個系統不能執行所要求的功能時,即為Failure,可譯為“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循環中的條件判斷應為:(int i=x.length-1; i > =0;i–);
2. If possible, identify a test case that does not execute the fault. (Reachability)
test: x=[];
(抛出空指針異常,沒有執行下面的程式,則沒有執行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
(執行了含有fault的程式,但是并沒有産生錯誤,即執行了fault,沒有執行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
(沒有周遊x=1,直接傳回了-1,是以執行了error,沒有執行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