[iOS] 养成TDD好习惯(1)：create first project with unit test

1. Create a projectwith ticking “include unit test” option inxcode.

* 生成的project会创建 2target, one for product app, one for unit test.

* For existingproject, to add unit test feature, just add a “unit testing bundle” type target

* By default, thereare 2 groups, one for product app, one for unit test. Unit test group里的.mfiles的property panel都是指向 unit test target。 而在product app group里的.mfiles都是指向product app target。不过2个group里的.hfiles都不指向任何target。有文章说对要被unit
test的需要同时指向2个target，但我试了一下，好像不需要。

2. 先说requirement，要创建一个class叫Calculator, 会包含一个加法的method。

3. TDD，先写unittest:

* right click the unit testgroup, select “New File > Cocoa touch > objective c test case class”,click “next”

* set “Class” as “CalculatorTests”,click “Next”

* make sure unit test target is ticked, group is unit test, andfile path in unit test folder

* 代码如下

//CalculatorTests.h

#import<SenTestingKit/SenTestingKit.h>

@class Calculator;

@interface CalculatorTests :
SenTestCase{

Calculator* calculator;

}

@end

//CalculatorTests.m

#import"CalculatorTests.h"

#import"Calculator.h"

@implementation CalculatorTests

-(void) setUp{

calculator = [[Calculator
alloc] init];

}

-(void) tearDown{

calculator =
nil;

}

@end

4. 上面代码编译错误，因为没有Calculatorclass存在。现在创建一个classnamed “Calculator”，记住target指向product app target。

5. 继续TDD, 添加下面测试加法method的代码 in CalculatorTest.m

-(void) testAdd {

STAssertEquals([calculator add:
2to:3], 5,
@"2 + 3 result should be5");

}

6. 编译错误，因为Calculator里没有add:to: method. 添加下列代码

-(int) add: (int)a to: (int)b{

return a + b;

}

7. 这时运行”Test”,如果failed, error list就会出现在左边的panel