【单元测试】C++单元测试框架Google Test入门之二：断言

- 日理万妓 2023-09-23 23:56 153阅读 0赞

#### 文章目录 ####

*  一、前言
 *  二、示例
 *  三、布尔值检查
 *  四、数值型数据检查
 *  五、字符串检查
 *  六、显示返回成功或失败
 *  七、异常检查
 *  八、Predicate Assertions
 *  九、浮点型检查
 *  十、Windows HRESULT assertions
 *  十一、类型检查
 *  十二、总结

## 一、前言 ##

这篇文章主要总结gtest中的所有断言相关的宏。 gtest中，断言的宏可以理解为分为两类，一类是ASSERT系列，一类是EXPECT系列。一个直观的解释就是：

1.  ASSERT\_\* 系列的断言，当检查点失败时，退出当前函数（注意：并非退出当前案例）。
2.  EXPECT\_\* 系列的断言，当检查点失败时，继续往下执行。

## 二、示例 ##

// int型比较，预期值：3，实际值：Add(1, 2)
    EXPECT_EQ(3, Add(1, 2))
    //

假如你的Add(1, 2) 结果为4的话，会在结果中输出：

g:\myproject\c++\gtestdemo\gtestdemo\gtestdemo.cpp(16): error: Value of: Add(1, 2)
      Actual: 4
    Expected:3

如果是将结果输出到xml里的话，将输出：（关于将结果输出为xml，见：）

如果你对自动输出的出错信息不满意的话，你还可以通过操作符<<将一些自定义的信息输出，通常，这对于调试或是对一些检查点的补充说明来说，非常有用！

下面举个例子：

如果不使用<<操作符自定义输出的话：

for (int i = 0; i < x.size(); ++i)
 {
 
 EXPECT_EQ(x[i], y[i]);
 }

看到的结果将是这样的，你根本不知道出错时 i 等于几：

g:\myproject\c++\gtestdemo\gtestdemo\gtestdemo.cpp(25): error: Value of: y[i]
      Actual: 4
    Expected: x[i]
    Which is: 3

如果使用<<操作符将一些重要信息输出的话：

for (int i = 0; i < x.size(); ++i)
 {
 
 EXPECT_EQ(x[i], y[i]) << "Vectors x and y differ at index " << i;
 }

从输出结果中就可以定位到在 i = 2 时出现了错误。这样的输出结果看起来更加有用，容易理解：

g:\myproject\c++\gtestdemo\gtestdemo\gtestdemo.cpp(25): error: Value of: y[i]
      Actual: 4
    Expected: x[i]
    Which is: 3
    Vectors x and y differ at index 2

## 三、布尔值检查 ##

<table> 
 <tbody> 
 <tr> 
 <td> Fatal assertion </td> 
 <td> Nonfatal assertion </td> 
 <td> Verifies </td> 
 </tr> 
 <tr> 
 <td> ASSERT_TRUE(condition); </td> 
 <td> EXPECT_TRUE(condition); </td> 
 <td> condition is true </td> 
 </tr> 
 <tr> 
 <td> ASSERT_FALSE(condition); </td> 
 <td> EXPECT_FALSE(condition); </td> 
 <td> condition is false </td> 
 </tr> 
 </tbody> 
</table>

## 四、数值型数据检查 ##

<table> 
 <tbody> 
 <tr> 
 <td> Fatal assertion </td> 
 <td> Nonfatal assertion </td> 
 <td> Verifies </td> 
 </tr> 
 <tr> 
 <td> ASSERT_EQ(expected, actual); </td> 
 <td> EXPECT_EQ(expected, actual); </td> 
 <td> expected == actual </td> 
 </tr> 
 <tr> 
 <td> ASSERT_NE(val1, val2); </td> 
 <td> EXPECT_NE(val1, val2); </td> 
 <td> val1 != val2 </td> 
 </tr> 
 <tr> 
 <td> ASSERT_LT(val1, val2); </td> 
 <td> EXPECT_LT(val1, val2); </td> 
 <td> val1 &lt; val2 </td> 
 </tr> 
 <tr> 
 <td> ASSERT_LE(val1, val2); </td> 
 <td> EXPECT_LE(val1, val2); </td> 
 <td> val1 &lt;= val2 </td> 
 </tr> 
 <tr> 
 <td> ASSERT_GT(val1, val2); </td> 
 <td> EXPECT_GT(val1, val2); </td> 
 <td> val1 &gt; val2 </td> 
 </tr> 
 <tr> 
 <td> ASSERT_GE(val1, val2); </td> 
 <td> EXPECT_GE(val1, val2); </td> 
 <td> val1 &gt;= val2 </td> 
 </tr> 
 </tbody> 
</table>

## 五、字符串检查 ##

<table> 
 <tbody> 
 <tr> 
 <td> Fatal assertion </td> 
 <td> Nonfatal assertion </td> 
 <td> Verifies </td> 
 </tr> 
 <tr> 
 <td> ASSERT_STREQ(expected_str, actual_str); </td> 
 <td> EXPECT_STREQ(expected_str, actual_str); </td> 
 <td> the two C strings have the same content </td> 
 </tr> 
 <tr> 
 <td> ASSERT_STRNE(str1, str2); </td> 
 <td> EXPECT_STRNE(str1, str2); </td> 
 <td> the two C strings have different content </td> 
 </tr> 
 <tr> 
 <td> ASSERT_STRCASEEQ(expected_str, actual_str); </td> 
 <td> EXPECT_STRCASEEQ(expected_str, actual_str); </td> 
 <td> the two C strings have the same content, ignoring case </td> 
 </tr> 
 <tr> 
 <td> ASSERT_STRCASENE(str1, str2); </td> 
 <td> EXPECT_STRCASENE(str1, str2); </td> 
 <td> the two C strings have different content, ignoring case </td> 
 </tr> 
 </tbody> 
</table>

\*\*STREQ\*\*和\*\*STRNE\*\*同时支持\*\*char\*\*\*和\*\*wchar\_t\*\*\*类型的，\*\*STRCASEEQ\*\*和\*\*STRCASENE\*\*却只接收\*\*char\*\*\*，估计是不常用吧。下面是几个例子：

TEST(StringCmpTest, Demo)
    {
        
        char* pszCoderZh = "CoderZh";
        wchar_t* wszCoderZh = L"CoderZh";
        std::string strCoderZh = "CoderZh";
        std::wstring wstrCoderZh = L"CoderZh";
    
        EXPECT_STREQ("CoderZh", pszCoderZh);
        EXPECT_STREQ(L"CoderZh", wszCoderZh);
    
        EXPECT_STRNE("CnBlogs", pszCoderZh);
        EXPECT_STRNE(L"CnBlogs", wszCoderZh);
    
        EXPECT_STRCASEEQ("coderzh", pszCoderZh);
        //EXPECT_STRCASEEQ(L"coderzh", wszCoderZh);    不支持
    
        EXPECT_STREQ("CoderZh", strCoderZh.c_str());
        EXPECT_STREQ(L"CoderZh", wstrCoderZh.c_str());
    }

## 六、显示返回成功或失败 ##

直接返回成功：SUCCEED();

返回失败：

<table> 
 <tbody> 
 <tr> 
 <td> Fatal assertion </td> 
 <td> Nonfatal assertion </td> 
 </tr> 
 <tr> 
 <td> FAIL(); </td> 
 <td> ADD_FAILURE(); </td> 
 </tr> 
 </tbody> 
</table>

TEST(ExplicitTest, Demo)
 {
 
 ADD_FAILURE() << "Sorry"; // None Fatal Asserton，继续往下执行。
 
 //FAIL(); // Fatal Assertion，不往下执行该案例。
 
 SUCCEED();
 }

## 七、异常检查 ##

<table> 
 <tbody> 
 <tr> 
 <td> Fatal assertion </td> 
 <td> Nonfatal assertion </td> 
 <td> Verifies </td> 
 </tr> 
 <tr> 
 <td> ASSERT_THROW(statement, exception_type); </td> 
 <td> EXPECT_THROW(statement, exception_type); </td> 
 <td> statement throws an exception of the given type </td> 
 </tr> 
 <tr> 
 <td> ASSERT_ANY_THROW(statement); </td> 
 <td> EXPECT_ANY_THROW(statement); </td> 
 <td> statement throws an exception of any type </td> 
 </tr> 
 <tr> 
 <td> ASSERT_NO_THROW(statement); </td> 
 <td> EXPECT_NO_THROW(statement); </td> 
 <td> statement doesn't throw any exception </td> 
 </tr> 
 </tbody> 
</table>

int Foo(int a, int b)
    {
        
        if (a == 0 || b == 0)
        {
        
            throw "don't do that";
        }
        int c = a % b;
        if (c == 0)
            return b;
        return Foo(b, c);
    }
    
    TEST(FooTest, HandleZeroInput)
    {
        
        EXPECT_ANY_THROW(Foo(10, 0));
        EXPECT_THROW(Foo(0, 5), char*);
    }

## 八、Predicate Assertions ##

在使用EXPECT\_TRUE或ASSERT\_TRUE时，有时希望能够输出更加详细的信息，比如检查一个函数的返回值TRUE还是FALSE时，希望能够输出传入的参数是什么，以便失败后好跟踪。因此提供了如下的断言：

<table> 
 <tbody> 
 <tr> 
 <td> Fatal assertion </td> 
 <td> Nonfatal assertion </td> 
 <td> Verifies </td> 
 </tr> 
 <tr> 
 <td> ASSERT_PRED1(pred1, val1); </td> 
 <td> EXPECT_PRED1(pred1, val1); </td> 
 <td> pred1(val1) returns true </td> 
 </tr> 
 <tr> 
 <td> ASSERT_PRED2(pred2, val1, val2); </td> 
 <td> EXPECT_PRED2(pred2, val1, val2); </td> 
 <td> pred2(val1, val2) returns true </td> 
 </tr> 
 <tr> 
 <td> ... </td> 
 <td> ... </td> 
 <td> ... </td> 
 </tr> 
 </tbody> 
</table>

Google人说了，他们只提供<=5个参数的，如果需要测试更多的参数，直接告诉他们。下面看看这个东西怎么用。

bool MutuallyPrime(int m, int n)
    {
        
        return Foo(m , n) > 1;
    }
    
    TEST(PredicateAssertionTest, Demo)
    {
        
        int m = 5, n = 6;
        EXPECT_PRED2(MutuallyPrime, m, n);
    }

当失败时，返回错误信息：

error: MutuallyPrime(m, n) evaluates to false, where  
m evaluates to 5  
n evaluates to 6

如果对这样的输出不满意的话，还可以自定义输出格式，通过如下：

<table> 
 <tbody> 
 <tr> 
 <td> Fatal assertion </td> 
 <td> Nonfatal assertion </td> 
 <td> Verifies </td> 
 </tr> 
 <tr> 
 <td> ASSERT_PRED_FORMAT1(pred_format1, val1); </td> 
 <td> EXPECT_PRED_FORMAT1(pred_format1, val1); </td> 
 <td> pred_format1(val1) is successful </td> 
 </tr> 
 <tr> 
 <td> ASSERT_PRED_FORMAT2(pred_format2, val1, val2); </td> 
 <td> EXPECT_PRED_FORMAT2(pred_format2, val1, val2); </td> 
 <td> pred_format2(val1, val2) is successful </td> 
 </tr> 
 <tr> 
 <td> ... </td> 
 <td> ... </td> 
 <td> ... </td> 
 </tr> 
 </tbody> 
</table>

用法示例：

testing::AssertionResult AssertFoo(const char* m_expr, const char* n_expr, const char* k_expr, int m, int n, int k) {
 
 if (Foo(m, n) == k)
 return testing::AssertionSuccess();
 testing::Message msg;
 msg << m_expr << " 和 " << n_expr << " 的最大公约数应该是：" << Foo(m, n) << " 而不是：" << k_expr;
 return testing::AssertionFailure(msg);
 }
 
 TEST(AssertFooTest, HandleFail)
 {
 
 EXPECT_PRED_FORMAT3(AssertFoo, 3, 6, 2);
 }

失败时，输出信息：

error: 3 和 6 的最大公约数应该是：3 而不是：2

是不是更温馨呢，呵呵。

## 九、浮点型检查 ##

<table> 
 <tbody> 
 <tr> 
 <td> Fatal assertion </td> 
 <td> Nonfatal assertion </td> 
 <td> Verifies </td> 
 </tr> 
 <tr> 
 <td> ASSERT_FLOAT_EQ(expected, actual); </td> 
 <td> EXPECT_FLOAT_EQ(expected, actual); </td> 
 <td> the two float values are almost equal </td> 
 </tr> 
 <tr> 
 <td> ASSERT_DOUBLE_EQ(expected, actual); </td> 
 <td> EXPECT_DOUBLE_EQ(expected, actual); </td> 
 <td> the two double values are almost equal </td> 
 </tr> 
 </tbody> 
</table>

对相近的两个数比较：

<table> 
 <tbody> 
 <tr> 
 <td> Fatal assertion </td> 
 <td> Nonfatal assertion </td> 
 <td> Verifies </td> 
 </tr> 
 <tr> 
 <td> ASSERT_NEAR(val1, val2, abs_error); </td> 
 <td> EXPECT_NEAR(val1, val2, abs_error); </td> 
 <td> the difference between val1 and val2 doesn't exceed the given absolute error </td> 
 </tr> 
 </tbody> 
</table>

同时，还可以使用：

EXPECT_PRED_FORMAT2(testing::FloatLE, val1, val2);
    EXPECT_PRED_FORMAT2(testing::DoubleLE, val1, val2);

## 十、Windows HRESULT assertions ##

<table> 
 <tbody> 
 <tr> 
 <td> Fatal assertion </td> 
 <td> Nonfatal assertion </td> 
 <td> Verifies </td> 
 </tr> 
 <tr> 
 <td> ASSERT_HRESULT_SUCCEEDED(expression); </td> 
 <td> EXPECT_HRESULT_SUCCEEDED(expression); </td> 
 <td> expression is a success HRESULT </td> 
 </tr> 
 <tr> 
 <td> ASSERT_HRESULT_FAILED(expression); </td> 
 <td> EXPECT_HRESULT_FAILED(expression); </td> 
 <td> expression is a failure HRESULT </td> 
 </tr> 
 </tbody> 
</table>

例如：

CComPtr shell;
    ASSERT_HRESULT_SUCCEEDED(shell.CoCreateInstance(L"Shell.Application"));
    CComVariant empty;
    ASSERT_HRESULT_SUCCEEDED(shell->ShellExecute(CComBSTR(url), empty, empty, empty, empty));

## 十一、类型检查 ##

类型检查失败时，直接导致代码编不过，难得用处就在这？看下面的例子：

template <typename T> class FooType {
 
 public:
 void Bar() {
 testing::StaticAssertTypeEq<int, T>(); }
 };
 
 TEST(TypeAssertionTest, Demo)
 {
 
 FooType<bool> fooType;
 fooType.Bar();
 }

## 十二、总结 ##

本篇将常用的断言都介绍了一遍，内容比较多，有些还是很有用的。要真的到写案例的时候，也行只是一两种是最常用的，现在时知道有这么多种选择，以后才方便查询。

【系列链接】  
[【单元测试】C++单元测试框架Google Test入门之一 : 初识Gtest][C_Google Test_ _ _Gtest]  
[【单元测试】C++单元测试框架Google Test入门之二 : 断言][C_Google Test_ _]  
[【单元测试】C++单元测试框架Google Test入门之三 : 事件机制][C_Google Test_ _ 1]  
[【单元测试】C++单元测试框架Google Test入门之四 : 参数化][C_Google Test_ _ 2]  
[【单元测试】C++单元测试框架Google Test入门之五 : 死亡测试][C_Google Test_ _ 3]  
[【单元测试】C++单元测试框架Google Test入门之六 : 运行参数][C_Google Test_ _ 4]  
[【单元测试】C++单元测试框架Google Test入门之七 : 深入解析GTEST][C_Google Test_ _ _GTEST]  
[【单元测试】C++单元测试框架Google Test入门之八 : 打造自己的单元测试框架][C_Google Test_ _ 5]

[C_Google Test_ _ _Gtest]: https://blog.csdn.net/weixin_43717839/article/details/128862746?spm=1001.2014.3001.5502
[C_Google Test_ _]: https://blog.csdn.net/weixin_43717839/article/details/128863859?spm=1001.2014.3001.5502
[C_Google Test_ _ 1]: https://blog.csdn.net/weixin_43717839/article/details/128896226?spm=1001.2014.3001.5502
[C_Google Test_ _ 2]: https://blog.csdn.net/weixin_43717839/article/details/128896292?spm=1001.2014.3001.5502
[C_Google Test_ _ 3]: https://blog.csdn.net/weixin_43717839/article/details/128896679?spm=1001.2014.3001.5502
[C_Google Test_ _ 4]: https://blog.csdn.net/weixin_43717839/article/details/128896931?spm=1001.2014.3001.5502
[C_Google Test_ _ _GTEST]: https://blog.csdn.net/weixin_43717839/article/details/128897405?spm=1001.2014.3001.5502
[C_Google Test_ _ 5]: https://blog.csdn.net/weixin_43717839/article/details/128897801?spm=1001.2014.3001.5502