断言

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。

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：http://www.cnblogs.com/coderzh/archive/2009/04/10/1432789.html）

<testcase name="Demo" status="run" time="0" classname="AddTest">      <failure message="Value of: Add(1, 2)
Actual: 4
Expected: 3" type=""><![CDATA[g:\myproject\c++\gtestdemo\gtestdemo\gtestdemo.cpp:16Value of: Add(1, 2)  Actual: 4Expected: 3]]></failure></testcase>

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

布尔值检查

Fatal assertion

Nonfatal assertion

Verifies

ASSERT_TRUE(condition);

EXPECT_TRUE(condition);

condition is true

ASSERT_FALSE(condition);

EXPECT_FALSE(condition);

condition is false

数值型数据检查

Fatal assertion

Nonfatal assertion

Verifies

ASSERT_EQ(expected, actual);

EXPECT_EQ(expected, actual);

expected == actual

ASSERT_NE(val1, val2);

EXPECT_NE(val1, val2);

val1 != val2

ASSERT_LT(val1, val2);

EXPECT_LT(val1, val2);

val1 < val2

ASSERT_LE(val1, val2);

EXPECT_LE(val1, val2);

val1 ⇐ val2

ASSERT_GT(val1, val2);

EXPECT_GT(val1, val2);

val1 > val2

ASSERT_GE(val1, val2);

EXPECT_GE(val1, val2);

val1 >= val2

字符串检查

Fatal assertion

Nonfatal assertion

Verifies

ASSERT_STREQ(expected_str, actual_str);

,EXPECT_STREQ(expected_str, actual_str);

,the two C strings have the same content

ASSERT_STRNE(str1, str2);

,EXPECT_STRNE(str1, str2);

,the two C strings have different content

ASSERT_STRCASEEQ(expected_str, actual_str);

,EXPECT_STRCASEEQ(expected_str, actual_str);

,the two C strings have the same content, ignoring case

ASSERT_STRCASENE(str1, str2);

,EXPECT_STRCASENE(str1, str2);

,the two C strings have different content, ignoring case

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());
}

显示返回成功或失败

直接返回成功：SUCCEED();

返回失败：

Fatal assertion

Nonfatal assertion

FAIL();,

ADD_FAILURE();

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();
}

异常检查

Fatal assertion

,Nonfatal assertion

,Verifies

ASSERT_THROW(statement, exception_type);

,EXPECT_THROW(statement, exception_type);

,statement throws an exception of the given type

ASSERT_ANY_THROW(statement);

,EXPECT_ANY_THROW(statement);

,statement throws an exception of any type

ASSERT_NO_THROW(statement);

,EXPECT_NO_THROW(statement);

,statement doesn’t throw any exception

例如：

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*);
}

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：

Fatal assertion

,Nonfatal assertion

,Verifies

ASSERT_PRED1(pred1, val1);

,EXPECT_PRED1(pred1, val1);

,pred1(val1) returns true

ASSERT_PRED2(pred2, val1, val2);

,EXPECT_PRED2(pred2, val1

, val2);,pred2(val1, val2) returns true

…​

,…​

,…​

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：

Fatal assertion

,Nonfatal assertion

,Verifies

ASSERT_PRED_FORMAT1(pred_format1, val1);

,EXPECT_PRED_FORMAT1(pred_format1, val1);

,pred_format1(val1) is successful

ASSERT_PRED_FORMAT2(pred_format2, val1, val2);

,EXPECT_PRED_FORMAT2(pred_format2, val1, val2);

,pred_format2(val1, val2) is successful

…​

,…​

,…​

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。

浮点型检查

Fatal assertion

,Nonfatal assertion

,Verifies

ASSERT_FLOAT_EQ(expected, actual);

,EXPECT_FLOAT_EQ(expected, actual);

,the two float values are almost equal

ASSERT_DOUBLE_EQ(expected, actual);

,EXPECT_DOUBLE_EQ(expected, actual);

,the two double values are almost equal

对相近的两个数比较：

Fatal assertion

,Nonfatal assertion

,Verifies

ASSERT_NEAR(val1, val2, abs_error);

,EXPECT_NEAR(val1, val2, abs_error);

,the difference between val1 and val2 doesn’t exceed the given absolute error

同时，还可以使用：

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

Windows HRESULT assertions

Fatal assertion

,Nonfatal assertion

,Verifies

ASSERT_HRESULT_SUCCEEDED(expression);

,EXPECT_HRESULT_SUCCEEDED(expression);

,expression is a success HRESULT

ASSERT_HRESULT_FAILED(expression);

,EXPECT_HRESULT_FAILED(expression);

,expression is a failure HRESULT

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));

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();
}

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。

Last moify: 2022-12-04 15:11:33
Build time：2025-07-18 09:41:42
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