1. 概要

在Linux系统中，进程的管理涉及到对进程状态的控制，特别是进程的冻结（暂停）和恢复（继续执行）功能对系统管理和调试非常重要。

本文将展示如何使用Google Test（gtest）编写针对进程冻结与恢复功能的单元测试。

• 完整代码见process_helper
• 提前阅读Linux C++编程-实现进程的冻结与恢复管理模块

2. 进程管理接口详解

2.1 进程冻结与恢复的基本概念

在Linux环境中，进程的管理涉及到对进程执行状态的控制，其中包括了进程的冻结（暂停）和恢复（继续执行）。这些操作通过发送特定的信号来实现，主要使用到 SIGSTOP 和 SIGCONT 信号。

2.2 进程查找与PID获取

为了准确控制目标进程，首先需要能够根据进程名称或者其他标识符获取到进程的PID。在Linux系统中，可以通过读取 /proc 文件系统来获取所有运行中进程的详细信息，包括进程的命令行参数和状态。

/*** @brief Function to find the PID of a process by its name* @param [in] processName  process name* @param [out] pid  process id* @return true - find pid by process name; false - not find pid by process name*/
bool FindPidByProcessName(const std::string& processName, pid_t &pid);

2.3 进程冻结与恢复的实现

2.3.1 进程冻结

进程冻结通过发送 SIGSTOP 信号来实现，暂停进程的执行。实现方法包括使用 kill(pid, SIGSTOP) 函数调用，并等待进程状态确认操作成功。

/*** @brief freeze process by pid** @param [in] pid - pid find by process name.* @return true - Freeze successfully; false - Freeze failed*/
bool FreezeProcessByPid(pid_t pid);

2.3.2 进程恢复

一旦进程被冻结，可以通过发送 SIGCONT 信号来恢复其执行。恢复过程中可能需要多次尝试，以确保进程成功从暂停状态恢复到执行状态。

/*** @brief try to resume a stopped process by pid** @param [in] attempts - if resume failed, try another attempts times.* @param [in] pid - pid find by process name.* @return true - Resume successfully; false - Resume failed*/
bool TryToResumeProcessByPid(pid_t pid, int attempts = 3);

2.4 进程终止

在某些情况下，需要强制终止一个进程以释放系统资源或确保安全性。可以使用 SIGKILL 信号立即终止进程的执行，但需要注意可能会造成数据丢失。

/*** @brief terminate a process** @param [in] processName - process name.* @param [in] attempts - if resume failed, try another attempts times.* @return 0 -  successfully; -1 - not found process; -2 terminate failed*         -3 - Handle waitpid error*/
int TerminateProcess(const std::string& processName, int attempts = 3);

2.5 进程状态监控与控制

在实现进程管理功能时，还需要监控进程的状态并根据需要进行控制。通过读取 /proc/[pid]/status 文件可以获取进程的详细状态信息，如是否处于停止状态。

/*** @brief Function to check if the process is not in stopped state** @param [in] pid - pid find by process name* @return true - stopped; false - not stopped*/
bool IsProcessStopped(pid_t pid);

确实，dummy_process是我们测试进程管理功能的一个重要组成部分。我们需要详细分析它的设计和实现，以便更好地理解整个测试框架。下面我们将详细介绍dummy_process的创建和管理过程，并分析其在单元测试中的作用。

3. dummy_process的设计与实现

为了测试进程管理功能，我们需要一个可以启动、冻结、恢复和终止的模拟进程。我们将创建一个名为dummy_process的shell脚本，该脚本将作为我们的模拟进程。通过这个脚本，我们可以在测试中验证进程管理功能的各个方面。

3.1 创建dummy_process脚本

dummy_process脚本是一个简单的无限循环脚本，它能够响应特定的信号（如SIGTERM）。我们使用C++程序来创建这个脚本，并确保它具有可执行权限。

void CreateDummyProcessScript(const std::string& scriptPath) {std::ofstream scriptFile(scriptPath);if (scriptFile.is_open()) {scriptFile << "#!/bin/bash\n";scriptFile << "\n";scriptFile << "# Function to handle signals\n";scriptFile << "function handle_signal() {\n";scriptFile << "    echo \"[dummy_process] Received signal: $1\"\n";scriptFile << "    exit 0\n";  // Exit gracefully on signalscriptFile << "}\n";scriptFile << "\n";scriptFile << "# Trap signals\n";scriptFile << "trap 'handle_signal SIGTERM' SIGTERM\n";  // Handle SIGTERM signalscriptFile << "\n";scriptFile << "# Main loop\n";scriptFile << "while true; do\n";scriptFile << "    echo \"dummy_process is running...\"\n";scriptFile << "    sleep 1\n";scriptFile << "done\n";scriptFile.close();// Add executable permission to the scriptif (chmod(scriptPath.c_str(), S_IRWXU | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH) == -1) {std::cerr << "Failed to set execute permission on " << scriptPath << std::endl;exit(EXIT_FAILURE);}} else {std::cerr << "Failed to create " << scriptPath << std::endl;exit(EXIT_FAILURE);}
}

3.2 启动dummy_process

在每个测试用例运行之前，我们需要启动dummy_process。这里我们使用fork()和execlp()函数来创建一个子进程，并在子进程中运行dummy_process脚本。

pid_t StartDummyProcess() {pid_t pid = fork();if (pid == -1) {std::cerr << "Failed to fork() process." << std::endl;return -1;} else if (pid == 0) {// Child process: execute dummy_process scriptexeclp(dummyScriptPath.c_str(), dummyScriptPath.c_str(), nullptr);// execlp should not return if successfulstd::cerr << "Failed to exec " << dummyScriptPath << std::endl;exit(EXIT_FAILURE);} else {// Parent process: return child process PIDreturn pid;}
}

3.3 终止dummy_process

在每个测试用例运行之后，我们需要终止dummy_process以清理环境。这里我们使用kill()函数发送SIGKILL信号，并使用waitpid()等待子进程终止。

void TerminateDummyProcess(pid_t pid) {// Send SIGKILL to dummy_processkill(pid, SIGKILL);// Wait for child process to endint status;waitpid(pid, &status, 0);
}

4. GTest单元测试代码详解

4.1 测试框架和测试结构

测试夹具 ProcessHelperTest 管理测试过程中的环境准备和清理工作，包括创建、启动和终止dummy_process。

class ProcessHelperTest : public ::testing::Test {protected:pid_t dummyProcessPid;std::string dummyScriptPath = "./dummy_process";  // Path to dummy_process shell scriptvoid SetUp() override {// 创建 dummy_process shell 脚本并启动CreateDummyProcessScript(dummyScriptPath);dummyProcessPid = StartDummyProcess();ASSERT_NE(dummyProcessPid, -1);  // 检查 dummy_process 启动成功}void TearDown() override {// 结束 dummy_processTerminateDummyProcess(dummyProcessPid);// 清理 dummy_process shell 脚本std::remove(dummyScriptPath.c_str());}
};

4.2 单元测试用例

4.2.1 测试冻结功能 FreezeProcessByPidTest

TEST_F(ProcessHelperTest, FreezeProcessByPidTest) {pid_t pid;bool find = FindPidByProcessName("dummy_process", pid);EXPECT_TRUE(find);  // 预期找到进程的PIDbool result = FreezeProcessByPid(pid);EXPECT_TRUE(result);  // 预期冻结操作成功ASSERT_TRUE(IsProcessRunning("dummy_process"));  // 检查进程仍在运行ASSERT_TRUE(IsProcessStopped(dummyProcessPid));  // 检查进程是否被成功冻结
}

4.2.2 测试恢复功能 TryToResumeProcessByPidTest

TEST_F(ProcessHelperTest, TryToResumeProcessByPidTest) {pid_t pid;bool find = FindPidByProcessName("dummy_process", pid);EXPECT_TRUE(find);  // 预期找到进程的PIDbool result = TryToResumeProcessByPid(pid, 3);EXPECT_TRUE(result);  // 预期恢复操作成功ASSERT_TRUE(IsProcessRunning("dummy_process"));  // 检查进程仍在运行ASSERT_FALSE(IsProcessStopped(dummyProcessPid));  // 检查进程是否已恢复执行
}

4.2.3 测试终止功能 TerminateProcessTest

TEST_F(ProcessHelperTest, TerminateProcessTest) {int result = TerminateProcess("dummy_process", 3);EXPECT_EQ(result, 0);  // 预期终止操作成功ASSERT_FALSE(IsProcessRunning("dummy_process"));  // 检查进程是否已终止
}

5. 运行和验证

测试程序的主函数调用了 RUN_ALL_TESTS() 来执行所有测试用例。在运行过程中，每个测试用例会被独立执行，并根据 EXPECT_ 和 ASSERT_ 宏的断言结果判断测试是否通过。

int main(int argc, char** argv) {testing::InitGoogleMock(&argc, argv);return RUN_ALL_TESTS();
}

单元测试结果:

$ ./process_helper_test 
[==========] Running 6 tests from 2 test suites.
[----------] Global test environment set-up.
[----------] 5 tests from ProcessHelperTest
[ RUN      ] ProcessHelperTest.FreezeProcessByNameTest
dummy_process is running...
Success to send SIGSTOP to process 12780
Process 12780 status is T is in stopped state.
Process 12780 freeze success.
processName dummy_process pid 12780 freeze success.
Process 12780 status is T is in stopped state.
[       OK ] ProcessHelperTest.FreezeProcessByNameTest (9 ms)
[ RUN      ] ProcessHelperTest.TryToResumeProcessByNameTest
dummy_process is running...
Process 12782 status is S is not in stopped state.
Process 12782 resumed successfully.
Process 12782 status is S is not in stopped state.
[       OK ] ProcessHelperTest.TryToResumeProcessByNameTest (25 ms)
[ RUN      ] ProcessHelperTest.FreezeProcessByPidTest
dummy_process is running...
Success to send SIGSTOP to process 12784
Process 12784 status is T is in stopped state.
Process 12784 freeze success.
Process 12784 status is T is in stopped state.
[       OK ] ProcessHelperTest.FreezeProcessByPidTest (14 ms)
[ RUN      ] ProcessHelperTest.TryToResumeProcessByPidTest
dummy_process is running...
Process 12786 status is S is not in stopped state.
Process 12786 resumed successfully.
Process 12786 status is S is not in stopped state.
[       OK ] ProcessHelperTest.TryToResumeProcessByPidTest (16 ms)
[ RUN      ] ProcessHelperTest.TerminateProcessTest
dummy_process is running...
Process with PID: 12788 has been terminated.
[       OK ] ProcessHelperTest.TerminateProcessTest (6 ms)
[----------] 5 tests from ProcessHelperTest (74 ms total)[----------] 1 test from IsProcessStoppedTest
[ RUN      ] IsProcessStoppedTest.IsStoppedTest
[       OK ] IsProcessStoppedTest.IsStoppedTest (0 ms)
[----------] 1 test from IsProcessStoppedTest (1 ms total)[----------] Global test environment tear-down
[==========] 6 tests from 2 test suites ran. (77 ms total)
[  PASSED  ] 6 tests.