# 4.4 使用Boost Test进行单元测试

**NOTE**:*此示例代码可以在* <https://github.com/dev-cafe/cmake-cookbook/tree/v1.0/chapter-04/recipe-04> *中找到，包含一个C++的示例。该示例在CMake 3.5版(或更高版本)中是有效的，并且已经在GNU/Linux、macOS和Windows上进行过测试。*

Boost Test是在C++社区中，一个非常流行的单元测试框架。本例中，我们将演示如何使用Boost Test，对求和示例代码进行单元测试。

## 准备工作

`main.cpp`、`sum_integers.cpp`和`sum_integers.hpp`与之前的示例相同，将更新`test.cpp`作为使用Boost Test库进行的单元测试：

```cpp
#include "sum_integers.hpp"

#include <vector>

#define BOOST_TEST_MODULE example_test_suite
#include <boost/test/unit_test.hpp>
BOOST_AUTO_TEST_CASE(add_example)
{
  auto integers = {1, 2, 3, 4, 5};
  auto result = sum_integers(integers);
  BOOST_REQUIRE(result == 15);
}
```

## 具体实施

以下是使用Boost Test构建项目的步骤:

1. 先从`CMakeLists.txt`开始:

   ```
   # set minimum cmake version
   cmake_minimum_required(VERSION 3.5 FATAL_ERROR)

   # project name and language
   project(recipe-04 LANGUAGES CXX)

   # require C++11
   set(CMAKE_CXX_STANDARD 11)
   set(CMAKE_CXX_EXTENSIONS OFF)
   set(CMAKE_CXX_STANDARD_REQUIRED ON)

   # example library
   add_library(sum_integers sum_integers.cpp)

   # main code
   add_executable(sum_up main.cpp)
   target_link_libraries(sum_up sum_integers)
   ```
2. 检测Boost库并将`cpp_test`链接到它:

   ```
   find_package(Boost 1.54 REQUIRED COMPONENTS unit_test_framework)

   add_executable(cpp_test test.cpp)

   target_link_libraries(cpp_test
     PRIVATE
       sum_integers
       Boost::unit_test_framework
     )

   # avoid undefined reference to "main" in test.cpp
   target_compile_definitions(cpp_test
     PRIVATE
         BOOST_TEST_DYN_LINK
     )
   ```
3. 最后，定义单元测试:

   ```
   enable_testing()

   add_test(
     NAME boost_test
     COMMAND $<TARGET_FILE:cpp_test>
     )
   ```
4. 下面是需要配置、构建和测试代码的所有内容:

   ```
   $ mkdir -p build
   $ cd build
   $ cmake ..
   $ cmake --build .
   $ ctest

   Test project /home/user/cmake-recipes/chapter-04/recipe-04/cxx-example/build
   Start 1: boost_test
   1/1 Test #1: boost_test ....................... Passed 0.01 sec
   100% tests passed, 0 tests failed out of 1
   Total Test time (real) = 0.01 sec

   $ ./cpp_test

   Running 1 test case...
   *** No errors detected
   ```

## 工作原理

使用`find_package`来检测Boost的`unit_test_framework`组件(参见第3章，第8节)。我们认为这个组件是`REQUIRED`的，如果在系统环境中找不到它，配置将停止。`cpp_test`目标需要知道在哪里可以找到Boost头文件，并且需要链接到相应的库；它们都由`IMPORTED`库目标`Boost::unit_test_framework`提供，该目标由`find_package`设置。

## 更多信息

本示例中，我们假设系统上安装了Boost。或者，我们可以在编译时获取并构建Boost依赖项。然而，Boost不是轻量级依赖项。我们的示例代码中，我们只使用了最基本的设施，但是Boost提供了丰富的特性和选项，有感兴趣的读者可以去这里看看：<http://www.boost.org/doc/libs/1_65_1/libs/test/doc/html/index.html> 。


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