Google C++单元测试框架GoogleTest---GTest的Sample1和编写单元测试的步骤

如果你还没有搭建gtest框架，可以参考我之前的博客：http://www.cnblogs.com/jycboy/p/6001153.html。。

1.The first sample: sample1

你把github上的项目导来之后，github地址：https://github.com/google/googletest，在目录：..(你的目录)\googletest-master\googletest\samples是你的samples文件夹。

在VS中创建项目：GtestSamples

把对应的代码加入到这里边：sample1.h、sample1.cc、sample1_unittest.cc.

在sample1.cc中是你要测试的函数：

// Returns n! (the factorial of n).  For negative n, n! is defined to be 1.
//
int Factorial(int n) {
	int result = 1;
	for (int i = 1; i <= n; i++) {
		result *= i;
	}

	return result;
}

// Returns true iff n is a prime number.
bool IsPrime(int n) {
	// Trivial case 1: small numbers
	if (n <= 1) return false;

	// Trivial case 2: even numbers
	if (n % 2 == 0) return n == 2;

	// Now, we have that n is odd and n >= 3.
	// Try to divide n by every odd number i, starting from 3
	for (int i = 3; ; i += 2) {
		// We only have to try i up to the squre root of n
		if (i > n / i) break;

		// Now, we have i <= n/i < n.
		// If n is divisible by i, n is not prime.
		if (n % i == 0) return false;
	}
	// n has no integer factor in the range (1, n), and thus is prime.
	return true;
}

在sample1_unittest.cc中，是你编写的测试：

有两个测试用例：Factorial、IsPrime;每个测试用例对应三个test。

extern int Factorial(int n);
extern bool IsPrime(int n);
// Tests Factorial().

// Tests factorial of negative numbers.
TEST(FactorialTest, Negative) {
	// This test is named "Negative", and belongs to the "FactorialTest"
	// test case.
	EXPECT_EQ(1, Factorial(-5));
	EXPECT_EQ(2, Factorial(-1)); //如果是ASSERT_EQ，后边的EXPECT_GT将不在执行；如果是EXPECT_EQ，后边的测试EXPECT_GT继续执行
	EXPECT_GT(Factorial(-10), 0);
	ASSERT_EQ(3, Factorial(-1));

	// <TechnicalDetails>
	//
	// EXPECT_EQ(expected, actual) is the same as
	//
	//   EXPECT_TRUE((expected) == (actual))
	//
	// except that it will print both the expected value and the actual
	// value when the assertion fails.  This is very helpful for
	// debugging.  Therefore in this case EXPECT_EQ is preferred.
	//
	// On the other hand, EXPECT_TRUE accepts any Boolean expression,
	// and is thus more general.
	//
	// </TechnicalDetails>
}

// Tests factorial of 0.
TEST(FactorialTest, Zero) {
	EXPECT_EQ(1, Factorial(0));
}

// Tests factorial of positive numbers.
TEST(FactorialTest, Positive) {
	EXPECT_EQ(1, Factorial(1));
	EXPECT_EQ(2, Factorial(2));
	EXPECT_EQ(6, Factorial(3));
	EXPECT_EQ(40320, Factorial(8));
}

// Tests IsPrime()

// Tests negative input.
TEST(IsPrimeTest, Negative) {
	// This test belongs to the IsPrimeTest test case.

	EXPECT_FALSE(IsPrime(-1));
	EXPECT_FALSE(IsPrime(-2));
	EXPECT_FALSE(IsPrime(INT_MIN));
}

// Tests some trivial cases.
TEST(IsPrimeTest, Trivial) {
	EXPECT_FALSE(IsPrime(0));
	EXPECT_FALSE(IsPrime(1));
	EXPECT_TRUE(IsPrime(2));
	EXPECT_TRUE(IsPrime(3));
}

// Tests positive input.
TEST(IsPrimeTest, Positive) {
	EXPECT_FALSE(IsPrime(4));
	EXPECT_TRUE(IsPrime(5));
	EXPECT_FALSE(IsPrime(6));
	EXPECT_TRUE(IsPrime(23));
}

// Step 3. Call RUN_ALL_TESTS() in main().
//
// We do this by linking in src/gtest_main.cc file, which consists of
// a main() function which calls RUN_ALL_TESTS() for us.
//
// This runs all the tests you've defined, prints the result, and
// returns 0 if successful, or 1 otherwise.
//
// Did you notice that we didn't register the tests?  The
// RUN_ALL_TESTS() macro magically knows about all the tests we
// defined.  Isn't this convenient?

　　

2.编写单元测试的步骤

Step 1.包括必要的头文件，以便声明测试逻辑需要的东西。不要忘了 gtest.h

#include <limits.h>
#include "sample1.h"
#include <gtest/gtest.h>

　Step 2. 使用TEST宏来定义测试。

TEST有两个参数：测试用例名称和测试名称。
使用宏后，应该在一对大括号之间定义测试逻辑。 您可以使用一堆宏来指示测试的成功或失败。 EXPECT_TRUE和EXPECT_EQ是此类宏的示例。 有关完整列表，请参阅gtest.h。

 技术细节：

在Google Test中，测试分为多个测试用例。你应该将逻辑相关的测试放入同一个测试用例。
测试用例名和测试名都应该是有效的C ++标识符。 并且你不应该在名称中使用下划线（_）。

Google测试保证您定义的每个测试只运行一次，但不能保证测试执行的顺序。 因此，您应该以这样一种方式编写测试，使得它们的结果不依赖于它们的顺序。

TEST(FactorialTest, Negative) {
  // This test is named "Negative", and belongs to the "FactorialTest"
  // test case.
  EXPECT_EQ(1, Factorial(-5));
  EXPECT_EQ(2, Factorial(-1)); //如果是ASSERT_EQ，后边的EXPECT_GT将不在执行；如果是EXPECT_EQ，后边的测试EXPECT_GT继续执行
  EXPECT_GT(Factorial(-10), 0);
  EXPECT_TRUE(2 == Factorial(-7));//这个错误失败信息打印的是true或false，不会打印值
  ASSERT_EQ(3, Factorial(-1));
}

技术细节：

上面的EXPECT_EQ(1, Factorial(-1))和EXPECT_TRUE(1==Factorial(-1))的作用是一样的，但是当失败时，EXPECT_EQ会打印期望值和实际值，而EXPECT_TRUE是会打印true、false。所以优先选用EXPECT_EQ。

Step 3. Call RUN_ALL_TESTS() in main().

int main(int argc, char **argv) {
//printf("Running main() from gtest_main.cc\n");
testing::InitGoogleTest(&argc,argv);
return RUN_ALL_TESTS();
}

　　 **RUN_ALL_TESTS() 会自动调用所有的测试。

之前的两篇博客：

VS2015搭建GoogleTest框架--配置第一个项目

Google C++单元测试框架---Gtest框架简介（译文）

之后会陆续更新，一直到GMock，但愿我不会太懒，。。。。