Google Test简述

Google Test简述

Google Test是谷歌推出的C++测试框架，谷歌出品，实力肯定是有保障的。官方文档在文章末尾。
如果可以还是建议看英文的源文档

特点

• 跨平台
• 不止单元测试
• 稳定并且可重复
• 提供足够的失败信息
• 快速
• 线程安全

支持的平台，编译器和构建系统
平台

• Linux
• macOS
• Windows

编译器

• gcc 5.0+
• clang 5.0+
• MSVC 2015+
  macOS users: Xcode 9.3+ provides clang 5.0+.

构建系统

• Bazel
• CMake

1.最简单的使用方法-cmake通过联网编译

注意此方法必须要联网的，因为是cmake直接从github上面拉取了googletest项目。
我是在mac os上测试的。
新建一个文件hello_test.cc

#include 

// Demonstrate some basic assertions.
TEST(HelloTest, BasicAssertions) {
  // Expect two strings not to be equal.
  EXPECT_STRNE("hello", "world");
  // Expect equality.
  EXPECT_EQ(7 * 6, 42);
}

新建一个文件CMakeLists.txt

cmake_minimum_required(VERSION 3.14)
project(my_project)

# GoogleTest requires at least C++14
set(CMAKE_CXX_STANDARD 14)

include(FetchContent)
FetchContent_Declare(
  googletest
  GIT_REPOSITORY https://github.com/google/googletest.git
  GIT_TAG release-1.12.1
)
# For Windows: Prevent overriding the parent project's compiler/linker settings
set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
FetchContent_MakeAvailable(googletest)
enable_testing()

add_executable(
  hello_test
  hello_test.cc
)
target_link_libraries(
  hello_test
  GTest::gtest_main
)

include(GoogleTest)
gtest_discover_tests(hello_test)

然后在当前目录执行

cmake -S . -B build

直接cmake --build build
这一步会生成可执行文件

最后 cd build && ctest, 这一步就是执行了。

到这里已经搭建了一个很简单的googletest程序

从这里可以学会cmake的搭建一个应用的步骤

cmake -S . -B build // 搭建项目到build目录
cmake --build build // 编译链接为二进制程序
cd build #然后可以执行程序了

2.源代码编译

Google Test不是一个header-only的库，所以需要编译，同时确保头文件在包含目录中。
本文讲诉使用cmake构建Google Test，如果没有下载源代码需要下载。并且googletest使用cmake构建，cmake是现代许多C/C++项目的构建器，掌握了是很有好处的，cmake相当于对MakeFile的封装，其实底层还是调用的gcc/g++等编译器。

使用cmake编译：

git clone https://github.com/google/googletest.git -b release-1.10.0 #拉取源代码
cd googletest        # Main directory of the cloned repository.
mkdir build          # Create a directory to hold the build output.
cd build
cmake ..             # Generate native build scripts for GoogleTest.

如果接着输入如下代码，就可以直接在build目录生成库了，-S是source的缩写代表源码路径，-B是build的缩写，代表生成路径

cmake -S . -B build

如果要编译为动态库，则

cmake -DGTEST_CREATE_SHARED_LIBRARY=1 -S . -B build

或者进入build打开sln文件即可用IDE编译。
库文件生成在build/lib目录下面，默认为静态库。头文件在googletest/include目录下面。
我这里是使用Xcode打开，

点击这个按钮就生成了文件

可以看到库文件已经生成

生成了库和头文件之后，就可以使用googletest了,windows平台下类似操作，使用Visual Studio生成项目文件，然后去目录中找到对应的头文件与库文件，最后将要测试的项目来编译就行了。

3. VS2019新建项目

还有一种windows上可以用的，在vs2019，我发现googletest是默认的项目模板之一，所以直接使用Visual Studio2019新建一个Google Test项目。如下图

测试代码示例

现有如下文件

sample1.h

#ifndef GOOGLETEST_SAMPLES_SAMPLE1_H_
#define GOOGLETEST_SAMPLES_SAMPLE1_H_

// Returns n! (the factorial of n).  For negative n, n! is defined to be 1.
int Factorial(int n);
#endif  // GOOGLETEST_SAMPLES_SAMPLE1_H_

sample2.cpp

#include "sample1.h"

// 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;
}

sample1_unittest.cpp

// Step 1. Include necessary header files such that the stuff your
// test logic needs is declared.
//
// Don't forget gtest.h, which declares the testing framework.
#include 
#include "sample1.h"
#include "gtest/gtest.h"
namespace {

// Step 2. Use the TEST macro to define your tests.
//
// TEST has two parameters: the test case name and the test name.
// After using the macro, you should define your test logic between a
// pair of braces.  You can use a bunch of macros to indicate the
// success or failure of a test.  EXPECT_TRUE and EXPECT_EQ are
// examples of such macros.  For a complete list, see gtest.h.
//
// 
//
// In Google Test, tests are grouped into test cases.  This is how we
// keep test code organized.  You should put logically related tests
// into the same test case.
//
// The test case name and the test name should both be valid C++
// identifiers.  And you should not use underscore (_) in the names.
//
// Google Test guarantees that each test you define is run exactly
// once, but it makes no guarantee on the order the tests are
// executed.  Therefore, you should write your tests in such a way
// that their results don't depend on their order.
//
// 


// 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(1, Factorial(-1));
  EXPECT_GT(Factorial(-10), 0);

  // 
  //
  // 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.
  //
  // 
}

// 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));
}

// 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?

Assertions 宏详解

Googletest 断言就是宏。通过断言测试一个函数或者类的行为。
出现错误时，googletest会打印源文件、代码行数和错误信息。
结果只有三种，分别是成功，非致命错误，致命错误，即success, nonfatal failure, fatal failure。非致命错误不会终止当前函数，致命错误会终止测试程序并且退出，也就是说接下来的测试就不会运行了。
一般使用EXPECT_*，这样可以跑完整个测试程序。

宏的格式有两种：

宏	产生效果
ASSERT_*	致命错误
EXPECT_*	非致命错误

一般来说，EXPECT_*用得更多，因为可显示的错误信息不止一个。除非某条件不成立，程序就无法运行时，就使用ASSERT__*。

使用<<运算符来打印错误信息，示例：

ASSERT_EQ(x.size(), y.size()) << "Vectors x and y are of unequal length";

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

Basic Assertions

最基础的真假条件判断

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

Binary Comparison

判断两个值

Fatal assertion	Nonfatal assertion	Verifies
ASSERT_EQ(val1, val2);	EXPECT_EQ(val1, val2);	val1 == val2
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

googletest官方文档

其实有一个更简单的方式，使用vcpkg，vcpkg是微软出的C++库管理器，非常好用。基本上流行的开源的库都有。
如何使用vcpkg在我的一篇文章中有，googletest使用vcpkg编译