Google C++ Testing Framework之断言

本节将会深入一步，了解 gTest 的断言机制。

开始。

1. 我们先从测试代码第一行开始：

TEST(IsPrimeTest, TrueCondition)

宏：

    TEST 是一个宏，有两个参数，googtest对其解释为：test_case_name , test_name 。

    EXPECT_TRUE，见字知义，用来比较所传递的参数是否返回 true 。类似的有EXPECT_FALSE。

另：googletest还包装了另一个宏 ASSERT_*, 与EXPECT_* 的区别是：

    ASSERT_*版本的断言失败时会产生致命失败，并结束当前函数，后面的语句将不会执行。

    EXPECT_*版本的断言产生非致命失败，不会中止当前函数，也就是说，案例继续往下执行。 

2. 常用断言如下：

<1>. 基本的true/false条件测试：

Fatal assertion	Nonfatal assertion	Verifies
ASSERT_TRUE(condition);	EXPECT_TRUE(condition);	condition is true
ASSERT_FALSE(condition);	EXPECT_FALSE(condition);	condition is false

<2>. 数值比较 测试：

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

<3>. 比较两个C字符串(即char*或wchar_t*)测试：

（如果需要比较两个字符串对象，则相应地使用EXPECT_EQ等等）

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

<4>. 显示成功或失败（AdvanceGuide）:

SUCCEED();

FAIL();

ADD_FAILURE();

ADD_FAILURE_AT("file_path", line_number);

<5>. 异常检查（AdvanceGuide）：

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

<6>. 使用已有的布尔型函数：

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
...	...	...

<7>. 还可自定义输出格式：

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
...	...	...

<8>. 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

    两个相近数比较。

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

<9>. 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

总结：

通过以上常用断言总结，我们可以看到，gTest提供了非常丰富的断言来帮助我们更好地执行测试，编写更高效的自动化测试代码。