# Helper Macros

也許你已注意到，實作fixture的static函數`suite()`是重覆、容易出錯的細節。參考`Writing test fixture`這篇，創造一系列隱藏實作`suite()`細節的marco。

接著，用這些macro再重寫ComplexNumberTest的程式碼:

```
#include <cppunit/extensions/HelperMacros.h>

class ComplexNumberTest : public CppUnit::TestFixture  {
```

首先，我們先宣告CPPUNIT\_TEST\_SUITE()，把class name當參數丟進macro。

```
CPPUNIT_TEST_SUITE( ComplexNumberTest );
```

省下在static suite()裡，建立CppUnit::TestSuite物件，建構子參數為class name這些細節。接著，用CPPUNIT\_TEST()宣告fixture裡的每一個test case。

```
CPPUNIT_TEST( testEquality );
CPPUNIT_TEST( testAddition );
```

最後，加上CPPUNIT\_TEST\_SUITE\_END()結束整個宣告。

```
CPPUNIT_TEST_SUITE_END();
```

重點來了！suite()函數的實作細節都省下來了。

```
static CppUnit::TestSuite *suite();
```

而fixture其它部份，保持不變:

```
private:
  Complex *m_10_1, *m_1_1, *m_11_2;
protected:
  void setUp()
  {
    m_10_1 = new Complex( 10, 1 );
    m_1_1 = new Complex( 1, 1 );
    m_11_2 = new Complex( 11, 2 );  
  }

  void tearDown() 
  {
    delete m_10_1;
    delete m_1_1;
    delete m_11_2;
  }

  void testEquality()
  {
    CPPUNIT_ASSERT( *m_10_1 == *m_10_1 );
    CPPUNIT_ASSERT( !(*m_10_1 == *m_11_2) );
  }

  void testAddition()
  {
    CPPUNIT_ASSERT( *m_10_1 + *m_1_1 == *m_11_2 );
  }
};
```

隱藏的細節還包含，加到suite(`CppUnit::TestSuite`)的TestCaller，它用的類別，就是fixture的類別名稱，以及在該類別裡的函數名稱。在這裡，指的是`ComplexNumberTest::testEquality`和`ComplexNumberTest::testAddition`。

`helper macro`已經幫你寫好一些常用的assertion。例如確認ComplexNumber在除以0時會throw出MathException。

* 在使用marco的suite段落中，加上CPPUNIT\_TEST\_EXCEPTION()，並且將test case函數名稱與預期會throw出來的exception型別當作參數丟進去。
* 撰寫test case函數

```
CPPUNIT_TEST_SUITE( ComplexNumberTest );
  //...
  CPPUNIT_TEST_EXCEPTION( testDivideByZeroThrows, MathException );
CPPUNIT_TEST_SUITE_END();

//...
  void testDivideByZeroThrows()
  {
    *m_10_1 / ComplexNumber(0);  // The following line should throw a MathException.
  }
```

如果預期的exception沒有throw出來，報告中會記錄asserttion failure，測試不通過。

## 譯註

* 原文: automatically implements the static suite() method. \
  &#x20;翻譯成:「可以隱藏static函數`suite()`的實作細節」意同「自動化實作....這個函數」好怪！所以這樣翻。
* 原文: "ComplexNumberTest.testEquality" and "ComplexNumberTest.testAddition"。\
  翻譯成:`ComplexNumberTest::testEquality`和`ComplexNumberTest::testAddition`。\
  在C++中，通常會用`::`接函數名稱，表示「類別裡的函數」；用`.`接函數名稱，表示「 物件裡的函數」
* comon應該是common的筆誤。
* [Writing test fixture](http://cppunit.sourceforge.net/doc/1.8.0/group___writing_test_fixture.html)


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