什麼是白箱測試

白箱測試就是Program裡面如何運作的是透明的可見的

主要用來測底下幾個測試類型

• Architectural testing
• Structural testing

主要使用人員類型

• Developers
• Testers in critical system
• Team cross functionality

白箱測試的方法

• Statement Coverage
• Decision Coverage
• Condition Coverage
• Path Coverage
• MCDC
• others

Statement Coverage

Statement指的是任一一行code
而statement coverage的目標是覆蓋所有code的statements，得到100%的statement coverage

Statement Coverage = no. of statements tests / total no. of statements

Example 1

if x > 7:
	print "hello"

Statement test 1:

x = 8
當給予x = 8時，會執行到所有的code，這時候就是100%的覆蓋率

Statement test2:

x = 5
當給予x=5時，只會執行第一行，這時候為50%的覆蓋率

Example 2

if x == 3:
	print "hey"
else:
	print "never mind"

Statement test:

在這個案例，沒辦法只使用一個test case就完成100% statement coverage，必須要至少兩個
x = 3, x= 5 達到100% Statement 覆蓋率

Example 3

if day == "Monday"
	then statement a
else
	statement b
end if
if day == Tuesday
	then statement c
end if

Statement test:

這種情形有很多的測試選擇，且沒有辦法用很少數的測項達到100%覆蓋率
至少會有兩個test cases

1. day = Monday
2. day = Tuesday

Example 4

Start
Do until B == C
	if today == Monday
		set A=1
	else if today == Wednesday
		set A=2, B=C
	end if;
	if B < C
		B = B + 1
	end if;
end loop
end

Statement test:

至少會有兩個test cases來達到100%覆蓋率

1. B < C, today = Monday
2. B not equal to C, today = Wednesday

Example 5

if Quantity >= 20
	Discount = 0.05
if Quantity >= 100
	Discount = 0.1

Statement test:

只要一個test case就達到100% Statement覆蓋率

1. Quantity = 105

Decision Coverage

有些地方會稱為Branch Coverage
decision是在code裡面，為if, while, do while, 等等的數量
Test all decision outcomes in your code

DC = Decision outcomes covered / Total no. of decision outcomes

Example 1

if x > 3
	print "hello"

Decision test

if會有兩種結果: yes or no
所以在這邊的coverage test要達到100%必須要有兩個測項

1. x = 5
2. x = 1

• 由此可知，有沒有可能只用1個test cases就可以達到100%的decision coverage?
  ans: 完 全 不 可 能!!
• Decision coverage 和 Statement coverage哪一個比較好?
  ans: Decision Coverage一定是比較好且較有效率，也是一種廣泛用在白箱測試的方式。而且100%的DC絕對也會是100%的SC。
  所以SC是DC的其中一個subset

Example 2

if day == "Monday"
	then statement a
else
	statement b
end if
if day == Tuesday
	then statement c
end if

Decision test

if會有兩種結果: yes or no，所以這邊總共有4個decisions
所以在這邊的coverage test要達到100%必須要有兩個測項

1. day = Monday
2. day = Tuesday

Example 3

Start
Do until B == C
	if today == Monday
		set A=1
	else if today == Wednesday
		set A=2, B=C
	end if;
	if B < C
		B = B + 1
	end if;
end loop
end

Decision test:

if和Do until會有兩種結果: yes or no，所以這邊總共有4個decisions

至少要有四個test cases來達到100%覆蓋率

Condition Coverage

Test each condition in the code in true & false cases
測試code裡面所有的true和false條件

Decision 和 Condition的差異?

• if x > 3 這樣會有兩個outcomes
  這個同時為Decision和Condition
• if (x > 3) or (y > 5)
  這也是decision，我們只要測試有沒有過這行decision而已
  而如果是condition，我們會測所有的condition，這邊總共有兩個 x>3和y>5的true和false結果
• if (Grade>90) or (Student has a sportive achievement) or (Student has a disability)
  這會測3個condition

Condition Coverage測試了每一個conditon在true和false的狀態

Example 1

read x
read y
if (x == 0) or (y > 0):
	y = y/x
else:
	x = y + 2
print(x)
print(y)

Condition test:

所以Condition coverage test要達到100%必須要有兩個測項

1. x = 5, y = 5
2. x = 5, y = -5

Example 2

if number of books > 8 or sum > 100
	extra discount

Condition test:

這邊有兩個condition
所以Condition coverage test要達到100%必須要有兩個測項

1. number of books = 10, sum = 150
2. number of books = 5, sum = 50

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