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本文主要用于介绍一个完整的 GTest + GMock 使用示例，涵盖了接口定义、Mock 类实现、被测试类、以及单元测试代码，展示了如何使用 GMock 模拟依赖并进行行为验证。

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项目结构

gtest_gmock_demo/
├── CMakeLists.txt
├── include/
│   └── database.h
|     └── user_service.h
├── src/
│   └── user_service.cpp
├── test/
│   ├── user_service_test.cpp
│   └── mock_database.h

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1. 接口定义：include/database.h

#pragma once
#include <string>class IDatabase {
public:virtual ~IDatabase() = default;virtual bool connect(const std::string& db_uri) = 0;virtual bool save_user(const std::string& username, int age) = 0;
};

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2. 业务实现：src/user_service.cpp

// include/user_service.h
#pragma once#include "database.h"class UserService {
public:UserService(IDatabase *db);bool register_user(const std::string& username, int age);private:IDatabase *db_;
};

// src/user_service.cpp
#include "user_service.h"UserService::UserService(IDatabase *db) : db_(db) {}bool UserService::register_user(const std::string& username, int age) {if (db_ == nullptr || username.empty() || age <= 0) {return false;}return db_->save_user(username, age);
}

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3. GMock 模拟类：test/mock_database.h

#pragma once
#include "database.h"
#include <gmock/gmock.h>class MockDatabase : public IDatabase {
public:MOCK_METHOD(bool, connect, (const std::string& db_uri), (override));MOCK_METHOD(bool, save_user, (const std::string& username, int age), (override));
};

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4. 单元测试：test/user_service_test.cpp

#include "mock_database.h"
#include "user_service.h" 
#include <gtest/gtest.h>TEST(UserServiceTest, RegisterUserSuccess) {MockDatabase mock_db;UserService service(&mock_db);// 设定期望：save_user 被调用一次，参数为 "alice", 30，返回 trueEXPECT_CALL(mock_db, save_user("alice", 30)).Times(1).WillOnce(::testing::Return(true));EXPECT_TRUE(service.register_user("alice", 30));
}TEST(UserServiceTest, RegisterUserFail_EmptyName) {MockDatabase mock_db;UserService service(&mock_db);// 不应调用 save_userEXPECT_CALL(mock_db, save_user(::testing::_, ::testing::_)).Times(0);EXPECT_FALSE(service.register_user("", 25));
}TEST(UserServiceTest, RegisterUserFail_NegativeAge) {MockDatabase mock_db;UserService service(&mock_db);EXPECT_CALL(mock_db, save_user(::testing::_, ::testing::_)).Times(0);EXPECT_FALSE(service.register_user("bob", -10));
}

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CMake 配置：CMakeLists.txt

cmake_minimum_required(VERSION 3.14)project(GTestGMockDemo)set(CMAKE_CXX_STANDARD 17)enable_testing()include_directories(include)include(FetchContent)
FetchContent_Declare(googletestURL https://github.com/google/googletest/archive/refs/heads/main.zip
)FetchContent_MakeAvailable(googletest)add_executable(unit_testssrc/user_service.cpptest/user_service_test.cpp
)target_link_libraries(unit_testsGTest::gtestGTest::gmockGTest::gtest_mainpthread
)add_test(NAME AllTests COMMAND unit_tests)

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编译和运行测试

mkdir build && cd build
cmake ..
make
./unit_tests

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相关知识点

模块	说明
IDatabase	依赖接口，用于隔离测试
MockDatabase	GMock 自动生成桩代码
UserService	被测试的业务逻辑
EXPECT_CALL	验证函数是否按预期调用