這兩天翻了下 Kent? Beck 的 Test-Driven Development By Example 感覺還不錯,第一部分的例子講的挺好,本來想歸納一下,貌似太長了,等有時間了再歸納下,最后看到了附錄里面的一個Fibonacci數列的例子感覺也有那么點TDD的味道在里面,總結分享一下:
讓我們從最簡單的fibonacci(0)=0開始吧,先寫測試如下:
import
?junit.framework.TestCase;????????
???????
public
?
class
?TestFibonacci?
extends
?TestCase?
{????????
????
public
?
void
?testFibonacci()
{????????
????????assertEquals(
0
,fibonacci(
0
));????????
????}
????????????
}
?????
添加fibonacci方法的簡單實現即可:
private
?
int
?fibonacci(
int
?i)?
{??????????????
????????
return
?
0
;????????
????}
??
很顯然順利通過了測試;
再加一個測試實現fibonacci(1)=1;如下:
import
?junit.framework.TestCase;????????
???????
public
?
class
?TestFibonacci?
extends
?TestCase?
{????????
????
public
?
void
?testFibonacci()
{????????
????????assertEquals(
0
,fibonacci(
0
));????????
????????assertEquals(
1
,fibonacci(
1
));????????
????}
????????????
}
???????
為了順利通過測試,只需簡單的改動下fibonacci方法實現即可;
private
?
int
?fibonacci(
int
?i)?
{??????????????
????????
if
(i
==
0
)?
return
?
0
;????????
????????
else
?
return
?
1
;????????
????}
???
在添加第三個測試條件fibonacci(2)=1時候發現,隨著測試條件的增多無疑帶來了大量的斷言重復代碼,通過分析我們可以將testFibonacci方法改寫如下:
public
?
void
?testFibonacci()
{????
????????
int
?cases[][]
=
{
{
0
,
0
}
,
{
1
,
1
}
}
;????
????????
for
(
int
?i
=
0
;i?
????????????assertEquals(cases[i][
1
],fibonacci(cases[i][
0
]));???????
????}
???
這樣我們就可以很容易的添加測試條件:fibonacci(2)=1;
import
?junit.framework.TestCase;????
???
public
?
class
?TestFibonacci?
extends
?TestCase?
{????
????
public
?
void
?testFibonacci()
{????
????????
int
?cases[][]
=
{
{
0
,
0
}
,
{
1
,
1
}
,
{
2
,
1
}
}
;????
????????
for
(
int
?i
=
0
;i?
????????????assertEquals(cases[i][
1
],fibonacci(cases[i][
0
]));???????
????}
????
???
????
private
?
int
?fibonacci(
int
?i)?
{??????????
????????
if
(i
==
0
)?
return
?
0
;????
????????
else
?
return
?
1
;????
????}
????
}
???
嘿嘿,很順利,狀態條依然出現的是綠色,那我們就不管代碼到底合不合理了,出現綠色就是王道,繼續添加下一個測試條件:fibonacci(3)=2;
import
?junit.framework.TestCase;????
???
public
?
class
?TestFibonacci?
extends
?TestCase?
{????
????
public
?
void
?testFibonacci()
{????
????????
int
?cases[][]
=
{
{
0
,
0
}
,
{
1
,
1
}
,
{
2
,
1
}
,
{
3
,
2
}
}
;????
????????
for
(
int
?i
=
0
;i?
????????????assertEquals(cases[i][
1
],fibonacci(cases[i][
0
]));???????
????}
????
???
????
private
?
int
?fibonacci(
int
?i)?
{??????????
????????
if
(i
==
0
)?
return
?
0
;????
????????
else
?
return
?
1
;????
????}
????
}
???
終于又出現紅色了,it fails .說明我們又將快有新進展了.為了滿足fibonacci(3)=2,也很簡單,簡單的修改下fibonacci方法即可,如下:
private?int?fibonacci(int?i)?{??????????
????????if(i==0)?return?0;????
????????if(i<=2)?return?1;????
????????else?return?2;????
????}?? 又出現綠色了吧! 這里返回的2可以表示為1+1;
我們可以寫成:
private?int?fibonacci(int?i)?{??????????
????????if(i==0)?return?0;????
????????if(i<=2)?return?1;????
????????else?return?fibonacci(i-1)+1;????
????}???
第二個1可以寫成fibonacci(i-2):
import?junit.framework.TestCase;????
???
public?class?TestFibonacci?extends?TestCase?{????
????public?void?testFibonacci(){????
????????int?cases[][]={{0,0},{1,1},{2,1},{3,2}};????
????????for(int?i=0;i?
????????????assertEquals(cases[i][1],fibonacci(cases[i][0]));???????
????}????
???
????private?int?fibonacci(int?i)?{??????????
????????if(i==0)?return?0;????
????????if(i==1)?return?1;????
????????else?return?fibonacci(i-1)+fibonacci(i-2);????
????}????
}???
再添加測試條件:fibonacci(4)=3;fibonacci(5)=5:
import?junit.framework.TestCase;????
???
public?class?TestFibonacci?extends?TestCase?{????
????public?void?testFibonacci(){????
????????int?cases[][]={{0,0},{1,1},{2,1},{3,2},{4,3},{5,5}};????
????????for(int?i=0;i?
????????????assertEquals(cases[i][1],fibonacci(cases[i][0]));???????
????}????
???
????private?int?fibonacci(int?i)?{??????????
????????if(i==0)?return?0;????
????????if(i==1)?return?1;????
????????else?return?fibonacci(i-1)+fibonacci(i-2);????
????}????
}? 依然是綠色,呵呵,我們得到了正確的Fibonacci數列,驅動源于測試.
附:
Fibonacci數列簡介:Fibonacci數列從第0項開始依次為0,1,1,2,3,5,8……的數列，它存在如下特點:第0,1個數為0,1。從第2個數開始，該數是前面兩個數之和。即該數列第n項的值滿足如下公式：
