diff --git a/CMakeLists.txt b/CMakeLists.txt
index bab2d56..03139c5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -2,6 +2,9 @@
 cmake_minimum_required(VERSION 3.10)
 project(PathEditor VERSION 3.0 LANGUAGES C)
 
+# 选项：是否构建测试
+option(BUILD_TESTS "Build unit tests" OFF)
+
 # 启用资源编译器以处理 .rc 文件
 enable_language(RC)
 
@@ -18,6 +21,7 @@ set(SOURCES
     src/utils/safe_string.c
     src/utils/logger.c
     src/utils/i18n.c
+    src/utils/error_code.c
     src/ui/ui_utils.c
     src/ui/dialogs.c
     src/ui/main_window.c
@@ -123,3 +127,9 @@ add_custom_command(TARGET ${PROJECT_NAME} POST_BUILD
     "$<TARGET_FILE_DIR:${PROJECT_NAME}>/locale"
     COMMENT "Copying locale directory to build directory..."
 )
+
+# 测试支持
+if(BUILD_TESTS)
+    enable_testing()
+    add_subdirectory(tests)
+endif()
diff --git a/include/controller/callbacks_internal.h b/include/controller/callbacks_internal.h
index d3aac5f..2735b67 100644
--- a/include/controller/callbacks_internal.h
+++ b/include/controller/callbacks_internal.h
@@ -3,6 +3,7 @@
 
 #include <iup.h>
 #include "core/app_context.h"
+#include "utils/i18n.h"
 
 // 内部辅助函数声明（供各 callbacks_*.c 文件共享）
 // 这些函数不对外暴露，仅在 controller 层内部使用
diff --git a/include/utils/error_code.h b/include/utils/error_code.h
index cc9cf85..080f417 100644
--- a/include/utils/error_code.h
+++ b/include/utils/error_code.h
@@ -15,6 +15,7 @@ typedef enum {
     ERR_INVALID_INDEX = -10     // 无效索引
 } ErrorCode;
 
+// 获取错误码的字符串表示（英文，用于日志）
 const char* error_code_to_string(ErrorCode code);
 
 #endif // ERROR_CODE_H
diff --git a/include/utils/string_ext.h b/include/utils/string_ext.h
index ab43b49..6f6df2e 100644
--- a/include/utils/string_ext.h
+++ b/include/utils/string_ext.h
@@ -27,4 +27,7 @@ char *wide_to_utf8(const wchar_t *wstr);
 wchar_t *utf8_to_wide(const char *str);
 char *stristr(const char *haystack, const char *needle);
 
+// 检查字符串列表中是否存在指定路径（不区分大小写）
+int string_list_contains(const StringList *list, const char *str);
+
 #endif // STRING_EXT_H
diff --git a/po/en_US.po b/po/en_US.po
index f910a95..26b4803 100644
--- a/po/en_US.po
+++ b/po/en_US.po
@@ -6,8 +6,8 @@ msgid ""
 msgstr ""
 "Project-Id-Version: PathEditor 3.0\n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2026-03-26 10:00+0800\n"
-"PO-Revision-Date: 2026-03-26 19:59+0800\n"
+"POT-Creation-Date: 2026-04-29 16:30+0800\n"
+"PO-Revision-Date: 2026-04-29 16:30+0800\n"
 "Last-Translator: LHY <3364451258@qq.com>\n"
 "Language-Team: English\n"
 "Language: en_US\n"
@@ -103,3 +103,287 @@ msgstr "Chinese (Simplified)"
 #: src/ui/dialogs.c
 msgid "English"
 msgstr "English"
+
+#: src/controller/callbacks_sys.c
+msgid "Administrator privileges are required to save changes!"
+msgstr "Administrator privileges are required to save changes!"
+
+#: src/controller/callbacks_sys.c
+msgid "Backup Settings"
+msgstr "Backup Settings"
+
+#: src/controller/callbacks_sys.c
+msgid "Would you like to customize the backup directory?"
+msgstr "Would you like to customize the backup directory?"
+
+#: src/controller/callbacks_sys.c
+msgid "Use Default"
+msgstr "Use Default"
+
+#: src/controller/callbacks_sys.c
+msgid "Custom Directory"
+msgstr "Custom Directory"
+
+#: src/controller/callbacks_sys.c
+msgid "Skip Backup"
+msgstr "Skip Backup"
+
+#: src/controller/callbacks_sys.c
+msgid "No directory selected, will use default backup path."
+msgstr "No directory selected, will use default backup path."
+
+#: src/controller/callbacks_sys.c
+msgid "Confirm"
+msgstr "Confirm"
+
+#: src/controller/callbacks_sys.c
+msgid "Are you sure you want to skip backup?"
+msgstr "Are you sure you want to skip backup?"
+
+#: src/controller/callbacks_sys.c
+msgid "Skipping backup may cause inability to recover!"
+msgstr "Skipping backup may cause inability to recover!"
+
+#: src/controller/callbacks_sys.c
+msgid "Skip Anyway"
+msgstr "Skip Anyway"
+
+#: src/controller/callbacks_sys.c
+msgid "Go Back"
+msgstr "Go Back"
+
+#: src/controller/callbacks_sys.c
+msgid "Continue Saving"
+msgstr "Continue Saving"
+
+#: src/controller/callbacks_sys.c
+msgid "Success"
+msgstr "Success"
+
+#: src/controller/callbacks_sys.c
+msgid "Both system and user PATH environment variables have been updated!"
+msgstr "Both system and user PATH environment variables have been updated!"
+
+#: src/controller/callbacks_sys.c
+msgid "Info"
+msgstr "Info"
+
+#: src/controller/callbacks_sys.c
+msgid "System variables saved successfully, but user variables failed to save."
+msgstr "System variables saved successfully, but user variables failed to save."
+
+#: src/controller/callbacks_sys.c
+msgid "User variables saved successfully, but system variables failed to save."
+msgstr "User variables saved successfully, but system variables failed to save."
+
+#: src/controller/callbacks_sys.c
+msgid "Failed to save!"
+msgstr "Failed to save!"
+
+#: src/controller/callbacks_sys.c
+msgid "Unable to open system environment variable registry key, please try running as administrator."
+msgstr "Unable to open system environment variable registry key, please try running as administrator."
+
+#: src/controller/callbacks_sys.c
+msgid "Usage Instructions"
+msgstr "Usage Instructions"
+
+#: src/controller/callbacks_sys.c
+msgid "This program is used to edit system environment variable PATH."
+msgstr "This program is used to edit system environment variable PATH."
+
+#: src/controller/callbacks_sys.c
+msgid "Must run as"
+msgstr "Must run as"
+
+#: src/controller/callbacks_sys.c
+msgid "Administrator"
+msgstr "Administrator"
+
+#: src/controller/callbacks_sys.c
+msgid "to save changes."
+msgstr "to save changes."
+
+#: src/controller/callbacks_sys.c
+msgid "Operations:"
+msgstr "Operations:"
+
+#: src/controller/callbacks_sys.c
+msgid "New: Add new path to end of list."
+msgstr "New: Add new path to end of list."
+
+#: src/controller/callbacks_sys.c
+msgid "Edit: Modify selected path."
+msgstr "Edit: Modify selected path."
+
+#: src/controller/callbacks_sys.c
+msgid "Browse: Select directory from file system to add."
+msgstr "Browse: Select directory from file system to add."
+
+#: src/controller/callbacks_sys.c
+msgid "Delete: Remove selected path."
+msgstr "Delete: Remove selected path."
+
+#: src/controller/callbacks_sys.c
+msgid "Up/Down: Adjust path priority."
+msgstr "Up/Down: Adjust path priority."
+
+#: src/controller/callbacks_sys.c
+msgid "Import/Export: Backup and restore PATH configuration."
+msgstr "Import/Export: Backup and restore PATH configuration."
+
+#: src/controller/callbacks_sys.c
+msgid "Click"
+msgstr "Click"
+
+#: src/controller/callbacks_sys.c
+msgid "to save changes and apply."
+msgstr "to save changes and apply."
+
+#: src/controller/callbacks_sys.c
+msgid "Note: Some running programs may need to restart to recognize new environment variables."
+msgstr "Note: Some running programs may need to restart to recognize new environment variables."
+
+#: src/controller/callbacks_sys.c
+msgid "Author: LHY"
+msgstr "Author: LHY"
+
+#: src/controller/callbacks_sys.c
+msgid "Email: 3364451258@qq.com"
+msgstr "Email: 3364451258@qq.com"
+
+#: src/controller/callbacks_sys.c
+msgid "GitHub: https://github.com/LHY0125/PathEditor"
+msgstr "GitHub: https://github.com/LHY0125/PathEditor"
+
+#: src/controller/callbacks_sys.c
+msgid "Don't forget to star my project!"
+msgstr "Don't forget to star my project!"
+
+#: src/controller/callbacks_io.c
+msgid "Administrator privileges are required to import PATH!"
+msgstr "Administrator privileges are required to import PATH!"
+
+#: src/controller/callbacks_io.c
+msgid "No valid paths found in file!"
+msgstr "No valid paths found in file!"
+
+#: src/controller/callbacks_io.c
+msgid "Import Options"
+msgstr "Import Options"
+
+#: src/controller/callbacks_io.c
+msgid "Please select import target:"
+msgstr "Please select import target:"
+
+#: src/controller/callbacks_io.c
+msgid "System Variables Only"
+msgstr "System Variables Only"
+
+#: src/controller/callbacks_io.c
+msgid "User Variables Only"
+msgstr "User Variables Only"
+
+#: src/controller/callbacks_io.c
+msgid "Import All"
+msgstr "Import All"
+
+#: src/controller/callbacks_io.c
+msgid "Import to System"
+msgstr "Import to System"
+
+#: src/controller/callbacks_io.c
+msgid "Import to User"
+msgstr "Import to User"
+
+#: src/controller/callbacks_io.c
+msgid "Successfully imported %d paths!"
+msgstr "Successfully imported %d paths!"
+
+#: src/controller/callbacks_io.c
+msgid "Import Success"
+msgstr "Import Success"
+
+#: src/controller/callbacks_io.c
+msgid "Import failed, please check if the file format is correct!"
+msgstr "Import failed, please check if the file format is correct!"
+
+#: src/controller/callbacks_io.c
+msgid "Export successful!"
+msgstr "Export successful!"
+
+#: src/controller/callbacks_io.c
+msgid "System variables: %d"
+msgstr "System variables: %d"
+
+#: src/controller/callbacks_io.c
+msgid "User variables: %d"
+msgstr "User variables: %d"
+
+#: src/controller/callbacks_io.c
+msgid "Save location: %s"
+msgstr "Save location: %s"
+
+#: src/controller/callbacks_io.c
+msgid "Export Success"
+msgstr "Export Success"
+
+#: src/controller/callbacks_io.c
+msgid "Export failed!"
+msgstr "Export failed!"
+
+#: src/controller/callbacks_nav.c
+msgid "Confirm Cleanup"
+msgstr "Confirm Cleanup"
+
+#: src/controller/callbacks_nav.c
+msgid "This operation will remove all"
+msgstr "This operation will remove all"
+
+#: src/controller/callbacks_nav.c
+msgid "invalid paths"
+msgstr "invalid paths"
+
+#: src/controller/callbacks_nav.c
+msgid "and"
+msgstr "and"
+
+#: src/controller/callbacks_nav.c
+msgid "duplicate paths"
+msgstr "duplicate paths"
+
+#: src/controller/callbacks_nav.c
+msgid "from the current list."
+msgstr "from the current list."
+
+#: src/controller/callbacks_nav.c
+msgid "Are you sure you want to continue?"
+msgstr "Are you sure you want to continue?"
+
+#: src/controller/callbacks_nav.c
+msgid "Cleanup completed! Removed %d invalid or duplicate paths."
+msgstr "Cleanup completed! Removed %d invalid or duplicate paths."
+
+#: src/controller/callbacks_basic.c
+msgid "New Environment Variable"
+msgstr "New Environment Variable"
+
+#: src/controller/callbacks_basic.c
+msgid "Please enter a path:"
+msgstr "Please enter a path:"
+
+#: src/controller/callbacks_basic.c
+msgid "Edit Environment Variable"
+msgstr "Edit Environment Variable"
+
+#: src/controller/callbacks_basic.c
+msgid "Edit path:"
+msgstr "Edit path:"
+
+#: src/controller/callbacks_basic.c
+msgid "Please select an item to delete first"
+msgstr "Please select an item to delete first"
+
+#: src/controller/callbacks_basic.c
+msgid "This path already exists and will not be added again."
+msgstr "This path already exists and will not be added again."
\ No newline at end of file
diff --git a/po/zh_CN.po b/po/zh_CN.po
index a04161f..c551280 100644
--- a/po/zh_CN.po
+++ b/po/zh_CN.po
@@ -6,8 +6,8 @@ msgid ""
 msgstr ""
 "Project-Id-Version: PathEditor 3.0\n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2026-03-26 10:00+0800\n"
-"PO-Revision-Date: 2026-03-26 19:58+0800\n"
+"POT-Creation-Date: 2026-04-29 16:30+0800\n"
+"PO-Revision-Date: 2026-04-29 16:30+0800\n"
 "Last-Translator: LHY <3364451258@qq.com>\n"
 "Language-Team: Chinese (Simplified)\n"
 "Language: zh_CN\n"
@@ -103,3 +103,287 @@ msgstr "中文 (简体中文)"
 #: src/ui/dialogs.c
 msgid "English"
 msgstr "English"
+
+#: src/controller/callbacks_sys.c
+msgid "Administrator privileges are required to save changes!"
+msgstr "需要管理员权限才能保存更改！"
+
+#: src/controller/callbacks_sys.c
+msgid "Backup Settings"
+msgstr "备份设置"
+
+#: src/controller/callbacks_sys.c
+msgid "Would you like to customize the backup directory?"
+msgstr "是否自定义备份目录？"
+
+#: src/controller/callbacks_sys.c
+msgid "Use Default"
+msgstr "使用默认"
+
+#: src/controller/callbacks_sys.c
+msgid "Custom Directory"
+msgstr "自定义目录"
+
+#: src/controller/callbacks_sys.c
+msgid "Skip Backup"
+msgstr "跳过备份"
+
+#: src/controller/callbacks_sys.c
+msgid "No directory selected, will use default backup path."
+msgstr "未选择目录，将使用默认备份路径。"
+
+#: src/controller/callbacks_sys.c
+msgid "Confirm"
+msgstr "确认"
+
+#: src/controller/callbacks_sys.c
+msgid "Are you sure you want to skip backup?"
+msgstr "确定跳过备份吗？"
+
+#: src/controller/callbacks_sys.c
+msgid "Skipping backup may cause inability to recover!"
+msgstr "跳过备份可能导致无法恢复！"
+
+#: src/controller/callbacks_sys.c
+msgid "Skip Anyway"
+msgstr "确定跳过"
+
+#: src/controller/callbacks_sys.c
+msgid "Go Back"
+msgstr "返回备份"
+
+#: src/controller/callbacks_sys.c
+msgid "Continue Saving"
+msgstr "继续保存"
+
+#: src/controller/callbacks_sys.c
+msgid "Success"
+msgstr "成功"
+
+#: src/controller/callbacks_sys.c
+msgid "Both system and user PATH environment variables have been updated!"
+msgstr "系统和用户 PATH 环境变量均已更新！"
+
+#: src/controller/callbacks_sys.c
+msgid "Info"
+msgstr "提示"
+
+#: src/controller/callbacks_sys.c
+msgid "System variables saved successfully, but user variables failed to save."
+msgstr "系统变量保存成功，但用户变量保存失败。"
+
+#: src/controller/callbacks_sys.c
+msgid "User variables saved successfully, but system variables failed to save."
+msgstr "用户变量保存成功，但系统变量保存失败。"
+
+#: src/controller/callbacks_sys.c
+msgid "Failed to save!"
+msgstr "保存失败！"
+
+#: src/controller/callbacks_sys.c
+msgid "Unable to open system environment variable registry key, please try running as administrator."
+msgstr "无法打开系统环境变量注册表键，请尝试以管理员身份运行。"
+
+#: src/controller/callbacks_sys.c
+msgid "Usage Instructions"
+msgstr "使用说明"
+
+#: src/controller/callbacks_sys.c
+msgid "This program is used to edit system environment variable PATH."
+msgstr "本程序用于编辑系统环境变量 PATH。"
+
+#: src/controller/callbacks_sys.c
+msgid "Must run as"
+msgstr "必须以"
+
+#: src/controller/callbacks_sys.c
+msgid "Administrator"
+msgstr "管理员身份"
+
+#: src/controller/callbacks_sys.c
+msgid "to save changes."
+msgstr "运行才能保存更改。"
+
+#: src/controller/callbacks_sys.c
+msgid "Operations:"
+msgstr "操作说明："
+
+#: src/controller/callbacks_sys.c
+msgid "New: Add new path to end of list."
+msgstr "新建：添加新路径到列表末尾。"
+
+#: src/controller/callbacks_sys.c
+msgid "Edit: Modify selected path."
+msgstr "编辑：修改选中的路径。"
+
+#: src/controller/callbacks_sys.c
+msgid "Browse: Select directory from file system to add."
+msgstr "浏览：从文件系统选择目录添加。"
+
+#: src/controller/callbacks_sys.c
+msgid "Delete: Remove selected path."
+msgstr "删除：移除选中的路径。"
+
+#: src/controller/callbacks_sys.c
+msgid "Up/Down: Adjust path priority."
+msgstr "上移/下移：调整路径优先级。"
+
+#: src/controller/callbacks_sys.c
+msgid "Import/Export: Backup and restore PATH configuration."
+msgstr "导入/导出：备份和恢复 PATH 配置。"
+
+#: src/controller/callbacks_sys.c
+msgid "Click"
+msgstr "点击"
+
+#: src/controller/callbacks_sys.c
+msgid "to save changes and apply."
+msgstr "保存更改并生效。"
+
+#: src/controller/callbacks_sys.c
+msgid "Note: Some running programs may need to restart to recognize new environment variables."
+msgstr "注意：某些正在运行的程序可能需要重启才能识别新的环境变量。"
+
+#: src/controller/callbacks_sys.c
+msgid "Author: LHY"
+msgstr "作者：LHY"
+
+#: src/controller/callbacks_sys.c
+msgid "Email: 3364451258@qq.com"
+msgstr "邮箱：3364451258@qq.com"
+
+#: src/controller/callbacks_sys.c
+msgid "GitHub: https://github.com/LHY0125/PathEditor"
+msgstr "GitHub：https://github.com/LHY0125/PathEditor"
+
+#: src/controller/callbacks_sys.c
+msgid "Don't forget to star my project!"
+msgstr "记得给我的项目点个star！"
+
+#: src/controller/callbacks_io.c
+msgid "Administrator privileges are required to import PATH!"
+msgstr "需要管理员权限才能导入 PATH！"
+
+#: src/controller/callbacks_io.c
+msgid "No valid paths found in file!"
+msgstr "文件中没有找到有效的路径！"
+
+#: src/controller/callbacks_io.c
+msgid "Import Options"
+msgstr "导入选项"
+
+#: src/controller/callbacks_io.c
+msgid "Please select import target:"
+msgstr "请选择导入目标："
+
+#: src/controller/callbacks_io.c
+msgid "System Variables Only"
+msgstr "仅系统变量"
+
+#: src/controller/callbacks_io.c
+msgid "User Variables Only"
+msgstr "仅用户变量"
+
+#: src/controller/callbacks_io.c
+msgid "Import All"
+msgstr "全部导入"
+
+#: src/controller/callbacks_io.c
+msgid "Import to System"
+msgstr "导入到系统变量"
+
+#: src/controller/callbacks_io.c
+msgid "Import to User"
+msgstr "导入到用户变量"
+
+#: src/controller/callbacks_io.c
+msgid "Successfully imported %d paths!"
+msgstr "成功导入 %d 个路径！"
+
+#: src/controller/callbacks_io.c
+msgid "Import Success"
+msgstr "导入成功"
+
+#: src/controller/callbacks_io.c
+msgid "Import failed, please check if the file format is correct!"
+msgstr "导入失败，请检查文件格式是否正确！"
+
+#: src/controller/callbacks_io.c
+msgid "Export successful!"
+msgstr "成功导出！"
+
+#: src/controller/callbacks_io.c
+msgid "System variables: %d"
+msgstr "系统变量: %d 个"
+
+#: src/controller/callbacks_io.c
+msgid "User variables: %d"
+msgstr "用户变量: %d 个"
+
+#: src/controller/callbacks_io.c
+msgid "Save location: %s"
+msgstr "保存位置: %s"
+
+#: src/controller/callbacks_io.c
+msgid "Export Success"
+msgstr "导出成功"
+
+#: src/controller/callbacks_io.c
+msgid "Export failed!"
+msgstr "导出失败！"
+
+#: src/controller/callbacks_nav.c
+msgid "Confirm Cleanup"
+msgstr "确认清理"
+
+#: src/controller/callbacks_nav.c
+msgid "This operation will remove all"
+msgstr "此操作将移除当前列表中所有"
+
+#: src/controller/callbacks_nav.c
+msgid "invalid paths"
+msgstr "无效路径"
+
+#: src/controller/callbacks_nav.c
+msgid "and"
+msgstr "和"
+
+#: src/controller/callbacks_nav.c
+msgid "duplicate paths"
+msgstr "重复路径"
+
+#: src/controller/callbacks_nav.c
+msgid "from the current list."
+msgstr "。"
+
+#: src/controller/callbacks_nav.c
+msgid "Are you sure you want to continue?"
+msgstr "确定要继续吗？"
+
+#: src/controller/callbacks_nav.c
+msgid "Cleanup completed! Removed %d invalid or duplicate paths."
+msgstr "清理完成！共移除了 %d 个无效或重复路径。"
+
+#: src/controller/callbacks_basic.c
+msgid "New Environment Variable"
+msgstr "新建环境变量"
+
+#: src/controller/callbacks_basic.c
+msgid "Please enter a path:"
+msgstr "请输入路径："
+
+#: src/controller/callbacks_basic.c
+msgid "Edit Environment Variable"
+msgstr "编辑环境变量"
+
+#: src/controller/callbacks_basic.c
+msgid "Edit path:"
+msgstr "编辑路径："
+
+#: src/controller/callbacks_basic.c
+msgid "Please select an item to delete first"
+msgstr "请先选择要删除的项"
+
+#: src/controller/callbacks_basic.c
+msgid "This path already exists and will not be added again."
+msgstr "该路径已存在，不会重复添加。"
\ No newline at end of file
diff --git a/src/controller/callbacks_basic.c b/src/controller/callbacks_basic.c
index 39868e0..db3bb9f 100644
--- a/src/controller/callbacks_basic.c
+++ b/src/controller/callbacks_basic.c
@@ -18,11 +18,19 @@ int btn_new_cb(Ihandle *self)
 {
     Ihandle *dlg = IupGetDialog(self);
     char buffer[PATH_BUFFER_SIZE] = "";
-    if (custom_input_dialog("新建环境变量", "请输入路径:", buffer, sizeof(buffer)))
+    if (custom_input_dialog(_("New Environment Variable"), _("Please enter a path:"), buffer, sizeof(buffer)))
     {
         if (strlen(buffer) > 0)
         {
             StringList *raw_data = get_current_raw_data(dlg);
+
+            // 检查是否已存在重复路径
+            if (string_list_contains(raw_data, buffer))
+            {
+                IupMessage(_("Warning"), _("This path already exists and will not be added again."));
+                return IUP_DEFAULT;
+            }
+
             add_string_list(raw_data, buffer);
 
             Ihandle *current_list = get_current_list(dlg);
@@ -51,7 +59,7 @@ int btn_edit_cb(Ihandle *self)
     char buffer[PATH_BUFFER_SIZE];
     safe_strcpy(buffer, sizeof(buffer), string_list_get(raw_data, selected - 1));
 
-    if (custom_input_dialog("编辑环境变量", "编辑路径:", buffer, sizeof(buffer)))
+    if (custom_input_dialog(_("Edit Environment Variable"), _("Edit path:"), buffer, sizeof(buffer)))
     {
         if (strlen(buffer) > 0)
         {
@@ -91,6 +99,15 @@ int btn_browse_cb(Ihandle *self)
         if (value)
         {
             StringList *raw_data = get_current_raw_data(dlg);
+
+            // 检查是否已存在重复路径
+            if (string_list_contains(raw_data, value))
+            {
+                IupMessage(_("Warning"), _("This path already exists and will not be added again."));
+                IupDestroy(filedlg);
+                return IUP_DEFAULT;
+            }
+
             add_string_list(raw_data, value);
 
             Ihandle *current_list = get_current_list(dlg);
@@ -113,7 +130,7 @@ int btn_del_cb(Ihandle *self)
 
     if (selected == 0)
     {
-        IupMessage("提示", "请先选择要删除的项");
+        IupMessage(_("Info"), _("Please select an item to delete first"));
         return IUP_DEFAULT;
     }
 
diff --git a/src/controller/callbacks_io.c b/src/controller/callbacks_io.c
index cb5fab0..0a55ce5 100644
--- a/src/controller/callbacks_io.c
+++ b/src/controller/callbacks_io.c
@@ -24,7 +24,7 @@ int btn_import_cb(Ihandle *self)
 
     if (!check_admin())
     {
-        IupMessage("错误", "需要管理员权限才能导入 PATH！");
+        IupMessage(_("Error"), _("Administrator privileges are required to import PATH!"));
         return IUP_DEFAULT;
     }
 
@@ -52,7 +52,7 @@ int btn_import_cb(Ihandle *self)
 
                 if (!has_system && !has_user)
                 {
-                    IupMessage("错误", "文件中没有找到有效的路径！");
+                    IupMessage(_("Error"), _("No valid paths found in file!"));
                     clear_string_list(&imported.system);
                     clear_string_list(&imported.user);
                     IupDestroy(filedlg);
@@ -62,14 +62,14 @@ int btn_import_cb(Ihandle *self)
                 int choice = 0;
                 if (has_system && has_user)
                 {
-                    choice = IupAlarm("导入选项", "请选择导入目标：",
-                                      "仅系统变量", "仅用户变量", "全部导入");
+                    choice = IupAlarm(_("Import Options"), _("Please select import target:"),
+                                      _("System Variables Only"), _("User Variables Only"), _("Import All"));
                 }
                 else if (has_system)
                 {
-                    // TXT 文件导入时，让用户选择目标（系统变量或用户变量）
-                    choice = IupAlarm("导入选项", "请选择导入目标：",
-                                      "导入到系统变量", "导入到用户变量", NULL);
+                    // TXT file import: let user choose target (system or user)
+                    choice = IupAlarm(_("Import Options"), _("Please select import target:"),
+                                      _("Import to System"), _("Import to User"), NULL);
                     // IupAlarm 返回 1 或 2，转换为 1(系统) 或 2(用户)
                 }
                 else
@@ -108,8 +108,8 @@ int btn_import_cb(Ihandle *self)
                 clear_string_list(&imported.user);
 
                 char msg[256];
-                snprintf(msg, sizeof(msg), "成功导入 %d 个路径！", total_imported);
-                IupMessage("导入成功", msg);
+                snprintf(msg, sizeof(msg), _("Successfully imported %d paths!"), total_imported);
+                IupMessage(_("Import Success"), msg);
 
                 Ihandle *lbl_status = IupGetDialogChild(dlg, CTRL_LBL_STATUS);
                 if (lbl_status)
@@ -118,7 +118,7 @@ int btn_import_cb(Ihandle *self)
             else
             {
                 log_error("Import failed: error code %d", import_result);
-                IupMessage("错误", "导入失败，请检查文件格式是否正确！");
+                IupMessage(_("Error"), _("Import failed, please check if the file format is correct!"));
             }
         }
     }
@@ -171,14 +171,14 @@ int btn_export_cb(Ihandle *self)
             if (export_result == ERR_OK)
             {
                 char msg[512];
-                snprintf(msg, sizeof(msg), "成功导出！\n系统变量: %d 个\n用户变量: %d 个\n\n保存位置: %s",
+                snprintf(msg, sizeof(msg), _("Export successful!\nSystem variables: %d\nUser variables: %d\n\nSave location: %s"),
                          data.system.count, data.user.count, filepath);
-                IupMessage("导出成功", msg);
+                IupMessage(_("Export Success"), msg);
             }
             else
             {
                 log_error("Export failed: error code %d", export_result);
-                IupMessage("错误", "导出失败！");
+                IupMessage(_("Error"), _("Export failed!"));
             }
         }
     }
diff --git a/src/controller/callbacks_nav.c b/src/controller/callbacks_nav.c
index f9407a7..b261321 100644
--- a/src/controller/callbacks_nav.c
+++ b/src/controller/callbacks_nav.c
@@ -61,7 +61,7 @@ int btn_clean_cb(Ihandle *self)
     if (!raw_data || raw_data->count == 0)
         return IUP_DEFAULT;
 
-    if (IupAlarm("确认清理", "此操作将移除当前列表中所有【无效路径】和【重复路径】。\n确定要继续吗？", "确定", "取消", NULL) != 1)
+    if (IupAlarm(_("Confirm Cleanup"), _("This operation will remove all 【invalid paths】 and 【duplicate paths】 from the current list.\nAre you sure you want to continue?"), _("Confirm"), _("Cancel"), NULL) != 1)
     {
         return IUP_DEFAULT;
     }
@@ -74,8 +74,8 @@ int btn_clean_cb(Ihandle *self)
     sync_string_list_to_ui(current_list, raw_data);
 
     char msg[128];
-    snprintf(msg, sizeof(msg), "清理完成！共移除了 %d 个无效或重复路径。", removed);
-    IupMessage("提示", msg);
+    snprintf(msg, sizeof(msg), _("Cleanup completed! Removed %d invalid or duplicate paths."), removed);
+    IupMessage(_("Info"), msg);
     return IUP_DEFAULT;
 }
 
diff --git a/src/controller/callbacks_sys.c b/src/controller/callbacks_sys.c
index 15fdf50..d717ac2 100644
--- a/src/controller/callbacks_sys.c
+++ b/src/controller/callbacks_sys.c
@@ -24,7 +24,7 @@ int btn_ok_cb(Ihandle *self)
 
     if (!check_admin())
     {
-        IupMessage("错误", "需要管理员权限才能保存更改！");
+        IupMessage(_("Error"), _("Administrator privileges are required to save changes!"));
         return IUP_DEFAULT;
     }
 
@@ -32,11 +32,11 @@ int btn_ok_cb(Ihandle *self)
     char custom_backup_dir[MAX_PATH] = "";
     int do_backup = 1;  // 是否执行备份
 
-    int backup_choice = IupAlarm("备份设置",
-                                  "是否自定义备份目录？\n\n"
-                                  "选择「使用默认」将备份到 %APPDATA%/PathEditor/backups/\n"
-                                  "选择「自定义目录」可选择其他位置",
-                                  "使用默认", "自定义目录", "跳过备份");
+    int backup_choice = IupAlarm(_("Backup Settings"),
+                                  _("Would you like to customize the backup directory?\n\n"
+                                    "Select 'Use Default' to backup to %%APPDATA%%/PathEditor/backups/\n"
+                                    "Select 'Custom Directory' to choose another location"),
+                                  _("Use Default"), _("Custom Directory"), _("Skip Backup"));
 
     if (backup_choice == 2)  // 自定义目录
     {
@@ -56,13 +56,13 @@ int btn_ok_cb(Ihandle *self)
 
         if (strlen(custom_backup_dir) == 0)
         {
-            IupMessage("提示", "未选择目录，将使用默认备份路径。");
+            IupMessage(_("Hint"), _("No directory selected, will use default backup path."));
         }
     }
     else if (backup_choice == 3)  // 跳过备份
     {
-        int skip_confirm = IupAlarm("确认", "确定跳过备份吗？\n跳过备份可能导致无法恢复！",
-                                    "确定跳过", "返回备份", NULL);
+        int skip_confirm = IupAlarm(_("Confirm"), _("Are you sure you want to skip backup?\nSkipping backup may cause inability to recover!"),
+                                    _("Skip Anyway"), _("Go Back"), NULL);
         if (skip_confirm != 1)
         {
             // 用户反悔，重新询问
@@ -89,7 +89,7 @@ int btn_ok_cb(Ihandle *self)
 
             char msg[512];
             snprintf(msg, sizeof(msg), "备份失败！原因：%s\n\n是否继续保存？\n（继续保存可能导致无法恢复）", reason);
-            int choice = IupAlarm("警告", msg, "继续保存", "取消", NULL);
+            int choice = IupAlarm(_("Warning"), msg, _("Continue Saving"), _("Cancel"), NULL);
             if (choice != 1)
                 return IUP_DEFAULT;
         }
@@ -104,22 +104,22 @@ int btn_ok_cb(Ihandle *self)
     {
         log_info("Saved system paths: %d, user paths: %d", ctx->sys_paths.count, ctx->user_paths.count);
         SendMessageTimeoutW(HWND_BROADCAST, WM_SETTINGCHANGE, 0, (LPARAM)L"Environment", SMTO_ABORTIFHUNG, 5000, NULL);
-        IupMessage("成功", "系统和用户 PATH 环境变量均已更新！");
+        IupMessage(_("Success"), _("Both system and user PATH environment variables have been updated!"));
         if (lbl_status)
             IupSetAttribute(lbl_status, "TITLE", lua_config_get_string("status", "saved"));
     }
     else if (sys_ok == ERR_OK)
     {
-        IupMessage("提示", "系统变量保存成功，但用户变量保存失败。");
+        IupMessage(_("Info"), _("System variables saved successfully, but user variables failed to save."));
     }
     else if (user_ok == ERR_OK)
     {
-        IupMessage("提示", "用户变量保存成功，但系统变量保存失败。");
+        IupMessage(_("Info"), _("User variables saved successfully, but system variables failed to save."));
     }
     else
     {
         log_error("Failed to save paths: sys=%d, user=%d", sys_ok, user_ok);
-        IupMessage("错误", "保存失败！");
+        IupMessage(_("Error"), _("Failed to save!"));
         if (lbl_status)
             IupSetAttribute(lbl_status, "TITLE", lua_config_get_string("status", "error"));
     }
@@ -146,7 +146,7 @@ void load_all_paths(void)
     if (load_system_paths(&ctx->sys_paths) != ERR_OK)
     {
         log_error("Failed to load system paths");
-        IupMessage("错误", "无法打开系统环境变量注册表键，请尝试以管理员身份运行。");
+        IupMessage(_("Error"), _("Unable to open system environment variable registry key, please try running as administrator."));
     }
     else
     {
@@ -182,23 +182,23 @@ int btn_lang_cb(Ihandle *self)
 // 按钮回调：帮助
 int btn_help_cb(Ihandle *self)
 {
-    IupMessage("使用说明",
-               "1. 本程序用于编辑系统环境变量 PATH。\n"
-               "2. 必须以【管理员身份】运行才能保存更改。\n"
-               "3. 操作说明：\n"
-               "   - 新建：添加新路径到列表末尾。\n"
-               "   - 编辑：修改选中的路径。\n"
-               "   - 浏览：从文件系统选择目录添加。\n"
-               "   - 删除：移除选中的路径。\n"
-               "   - 上移/下移：调整路径优先级。\n"
-               "   - 导入/导出：备份和恢复 PATH 配置。\n"
-               "4. 点击【确定】保存更改并生效。\n"
-               "5. 注意：某些正在运行的程序可能需要重启才能识别新的环境变量。\n\n"
-               "--------------------------------------------------\n"
-               "作者：LHY\n"
-               "邮箱：3364451258@qq.com\n"
-               "GitHub：https://github.com/LHY0125/PathEditor\n"
-               "记得给我的项目点个star！");
+    IupMessage(_("Usage Instructions"),
+               _("1. This program is used to edit system environment variable PATH.\n"
+                 "2. Must run as 【Administrator】 to save changes.\n"
+                 "3. Operations:\n"
+                 "   - New: Add new path to end of list.\n"
+                 "   - Edit: Modify selected path.\n"
+                 "   - Browse: Select directory from file system to add.\n"
+                 "   - Delete: Remove selected path.\n"
+                 "   - Up/Down: Adjust path priority.\n"
+                 "   - Import/Export: Backup and restore PATH configuration.\n"
+                 "4. Click 【OK】 to save changes and apply.\n"
+                 "5. Note: Some running programs may need to restart to recognize new environment variables.\n\n"
+                 "--------------------------------------------------\n"
+                 "Author: LHY\n"
+                 "Email: 3364451258@qq.com\n"
+                 "GitHub: https://github.com/LHY0125/PathEditor\n"
+                 "Don't forget to star my project!"));
 
     return IUP_DEFAULT;
 }
diff --git a/src/utils/error_code.c b/src/utils/error_code.c
new file mode 100644
index 0000000..2e8e145
--- /dev/null
+++ b/src/utils/error_code.c
@@ -0,0 +1,40 @@
+#include "utils/error_code.h"
+#include <string.h>
+
+const char* error_code_to_string(ErrorCode code)
+{
+    switch (code)
+    {
+        case ERR_OK:
+            return "Success";
+        case ERR_FAILED:
+            return "Operation failed";
+        case ERR_NULL_PTR:
+            return "Null pointer error";
+        case ERR_OUT_OF_MEMORY:
+            return "Out of memory";
+        case ERR_FILE_NOT_FOUND:
+            return "File not found";
+        case ERR_PERMISSION_DENIED:
+            return "Permission denied";
+        case ERR_INVALID_FORMAT:
+            return "Invalid format";
+        case ERR_REGISTRY_FAILED:
+            return "Registry operation failed";
+        case ERR_NOT_FOUND:
+            return "Item not found";
+        case ERR_EXISTS:
+            return "Item already exists";
+        case ERR_INVALID_INDEX:
+            return "Invalid index";
+        default:
+            return "Unknown error";
+    }
+}
+
+// 注意：error_code_to_message 需要链接 intl 库，
+// 如果不需要在错误码模块使用国际化，可以直接使用 error_code_to_string
+const char* error_code_to_message(ErrorCode code)
+{
+    return error_code_to_string(code);
+}
\ No newline at end of file
diff --git a/src/utils/string_ext.c b/src/utils/string_ext.c
index fdcfcc8..fd8a096 100644
--- a/src/utils/string_ext.c
+++ b/src/utils/string_ext.c
@@ -126,4 +126,17 @@ void clear_string_list(StringList *list)
     list->items = NULL;
     list->count = 0;
     list->capacity = 0;
+}
+
+// 检查字符串列表中是否存在指定路径（不区分大小写）
+int string_list_contains(const StringList *list, const char *str)
+{
+    if (!list || !str)
+        return 0;
+    for (int i = 0; i < list->count; i++)
+    {
+        if (list->items[i] && _stricmp(list->items[i], str) == 0)
+            return 1;
+    }
+    return 0;
 }
\ No newline at end of file
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
new file mode 100644
index 0000000..cbaf685
--- /dev/null
+++ b/tests/CMakeLists.txt
@@ -0,0 +1,40 @@
+# PathEditor 单元测试框架
+cmake_minimum_required(VERSION 3.10)
+
+# 测试子项目配置
+project(PathEditorTests C)
+
+# 设置 C 标准（与主项目一致）
+set(CMAKE_C_STANDARD 17)
+set(CMAKE_C_STANDARD_REQUIRED ON)
+set(CMAKE_C_EXTENSIONS OFF)
+
+# 包含主项目的头文件路径
+include_directories(
+    ${CMAKE_SOURCE_DIR}/include
+    ${CMAKE_SOURCE_DIR}/include/core
+    ${CMAKE_SOURCE_DIR}/include/ui
+    ${CMAKE_SOURCE_DIR}/include/controller
+    ${CMAKE_SOURCE_DIR}/include/utils
+    ${CMAKE_SOURCE_DIR}/libs/IUP/include
+    ${CMAKE_SOURCE_DIR}/libs/lua/include
+    ${CMAKE_SOURCE_DIR}/libs/gettext/include
+)
+
+# 获取 CMocka（如果系统没有则下载）
+include(FetchContent)
+FetchContent_Declare(
+    cmocka
+    GIT_REPOSITORY https://git.cryptomilk.org/projects/cmocka.git
+    GIT_TAG cmocka-1.1.5
+)
+FetchContent_MakeAvailable(cmocka)
+
+# 启用测试
+enable_testing()
+include(CTest)
+
+# 添加各测试模块
+add_subdirectory(unit/safe_string)
+add_subdirectory(unit/string_ext)
+add_subdirectory(unit/path_manager)
diff --git a/tests/mocks/mock_windows.h b/tests/mocks/mock_windows.h
new file mode 100644
index 0000000..e8f80fa
--- /dev/null
+++ b/tests/mocks/mock_windows.h
@@ -0,0 +1,54 @@
+/*
+ * mock_windows.h
+ * Windows API Mock 头文件
+ * 用于单元测试中模拟 Windows API
+ */
+#ifndef MOCK_WINDOWS_H
+#define MOCK_WINDOWS_H
+
+#ifdef TESTING
+
+#include <windows.h>
+#include <wchar.h>
+
+/* Mock 计数器，用于验证调用 */
+extern int mock_MultiByteToWideChar_call_count;
+extern int mock_WideCharToMultiByte_call_count;
+
+/* 设置 Mock 返回值 */
+void mock_set_MultiByteToWideChar_return(int ret);
+void mock_set_WideCharToMultiByte_return(int ret);
+
+/* Mock MultiByteToWideChar */
+int mock_MultiByteToWideChar(
+    UINT CodePage,
+    DWORD dwFlags,
+    LPCSTR lpMultiByteStr,
+    int cbMultiByte,
+    LPWSTR lpWideCharStr,
+    int cchWideChar);
+
+/* Mock WideCharToMultiByte */
+int mock_WideCharToMultiByte(
+    UINT CodePage,
+    DWORD dwFlags,
+    LPCWSTR lpWideCharStr,
+    int cchWideChar,
+    LPSTR lpMultiByteStr,
+    int cbMultiByte,
+    LPCSTR lpDefaultChar,
+    LPBOOL lpUsedDefaultChar);
+
+/* 替换宏（在测试源文件中定义） */
+#ifdef REPLACE_WINDOWS_API
+    #define MultiByteToWideChar mock_MultiByteToWideChar
+    #define WideCharToMultiByte mock_WideCharToMultiByte
+#endif
+
+#else
+/* 非测试模式下为空 */
+#define REPLACE_WINDOWS_API 0
+
+#endif /* TESTING */
+
+#endif /* MOCK_WINDOWS_H */
diff --git a/tests/unit/path_manager/CMakeLists.txt b/tests/unit/path_manager/CMakeLists.txt
new file mode 100644
index 0000000..cf15f63
--- /dev/null
+++ b/tests/unit/path_manager/CMakeLists.txt
@@ -0,0 +1,20 @@
+# path_manager 单元测试
+add_executable(test_path_manager test_path_manager.c
+    ${CMAKE_SOURCE_DIR}/src/core/path_manager.c
+    ${CMAKE_SOURCE_DIR}/src/utils/string_ext.c
+    ${CMAKE_SOURCE_DIR}/src/utils/safe_string.c
+    ${CMAKE_SOURCE_DIR}/src/utils/error_code.c
+)
+
+target_link_libraries(test_path_manager cmocka)
+
+target_include_directories(test_path_manager PRIVATE
+    ${CMAKE_SOURCE_DIR}/src/core
+    ${CMAKE_SOURCE_DIR}/src/utils
+)
+
+# 定义 TESTING 宏以启用 mock
+target_compile_definitions(test_path_manager PRIVATE TESTING)
+
+# 添加测试
+add_test(NAME path_manager_test COMMAND test_path_manager)
diff --git a/tests/unit/path_manager/test_path_manager.c b/tests/unit/path_manager/test_path_manager.c
new file mode 100644
index 0000000..8b1edf8
--- /dev/null
+++ b/tests/unit/path_manager/test_path_manager.c
@@ -0,0 +1,359 @@
+/*
+ * path_manager.c 单元测试
+ * 测试路径管理函数
+ */
+#include <stdarg.h>
+#include <stddef.h>
+#include <setjmp.h>
+#include <cmocka.h>
+#include <string.h>
+#include <stdlib.h>
+#include "core/path_manager.h"
+
+/* ==================== Mock 函数 ==================== */
+
+#ifdef TESTING
+
+/* Mock is_path_valid - 默认返回 1（有效）*/
+int is_path_valid_mock_enabled = 0;
+int is_path_valid_mock_return = 1;
+
+int is_path_valid(const char *path)
+{
+    (void)path;
+    if (is_path_valid_mock_enabled) {
+        return is_path_valid_mock_return;
+    }
+    return 1;  /* 默认认为路径有效 */
+}
+
+/* Mock 日志函数 - 避免链接日志文件依赖 */
+int log_info_enabled = 0;
+int log_debug_enabled = 0;
+int log_warn_enabled = 0;
+int log_error_enabled = 0;
+
+void log_info(const char *fmt, ...)
+{
+    (void)fmt;
+    log_info_enabled++;
+}
+
+void log_debug(const char *fmt, ...)
+{
+    (void)fmt;
+    log_debug_enabled++;
+}
+
+void log_warn(const char *fmt, ...)
+{
+    (void)fmt;
+    log_warn_enabled++;
+}
+
+void log_error(const char *fmt, ...)
+{
+    (void)fmt;
+    log_error_enabled++;
+}
+
+#endif /* TESTING */
+
+/* ==================== path_manager_remove_at 测试 ==================== */
+
+static void test_remove_at_normal(void **state)
+{
+    (void)state;
+    StringList list;
+    init_string_list(&list);
+    add_string_list(&list, "path1");
+    add_string_list(&list, "path2");
+    add_string_list(&list, "path3");
+
+    ErrorCode result = path_manager_remove_at(&list, 1);
+
+    assert_int_equal(result, ERR_OK);
+    assert_int_equal(list.count, 2);
+    assert_string_equal(string_list_get(&list, 0), "path1");
+    assert_string_equal(string_list_get(&list, 1), "path3");
+
+    clear_string_list(&list);
+}
+
+static void test_remove_at_first(void **state)
+{
+    (void)state;
+    StringList list;
+    init_string_list(&list);
+    add_string_list(&list, "path1");
+    add_string_list(&list, "path2");
+
+    ErrorCode result = path_manager_remove_at(&list, 0);
+
+    assert_int_equal(result, ERR_OK);
+    assert_int_equal(list.count, 1);
+    assert_string_equal(string_list_get(&list, 0), "path2");
+
+    clear_string_list(&list);
+}
+
+static void test_remove_at_last(void **state)
+{
+    (void)state;
+    StringList list;
+    init_string_list(&list);
+    add_string_list(&list, "path1");
+    add_string_list(&list, "path2");
+
+    ErrorCode result = path_manager_remove_at(&list, 1);
+
+    assert_int_equal(result, ERR_OK);
+    assert_int_equal(list.count, 1);
+    assert_string_equal(string_list_get(&list, 0), "path1");
+
+    clear_string_list(&list);
+}
+
+static void test_remove_at_invalid_index(void **state)
+{
+    (void)state;
+    StringList list;
+    init_string_list(&list);
+    add_string_list(&list, "path1");
+
+    ErrorCode result = path_manager_remove_at(&list, 5);  /* 越界 */
+
+    assert_int_not_equal(result, ERR_OK);
+
+    clear_string_list(&list);
+}
+
+static void test_remove_at_null(void **state)
+{
+    (void)state;
+    ErrorCode result = path_manager_remove_at(NULL, 0);
+    assert_int_equal(result, ERR_NULL_PTR);
+}
+
+/* ==================== path_manager_move_up 测试 ==================== */
+
+static void test_move_up_normal(void **state)
+{
+    (void)state;
+    StringList list;
+    init_string_list(&list);
+    add_string_list(&list, "path1");
+    add_string_list(&list, "path2");
+    add_string_list(&list, "path3");
+
+    ErrorCode result = path_manager_move_up(&list, 2);
+
+    assert_int_equal(result, ERR_OK);
+    assert_string_equal(string_list_get(&list, 0), "path1");
+    assert_string_equal(string_list_get(&list, 1), "path3");
+    assert_string_equal(string_list_get(&list, 2), "path2");
+
+    clear_string_list(&list);
+}
+
+static void test_move_up_first_element(void **state)
+{
+    (void)state;
+    StringList list;
+    init_string_list(&list);
+    add_string_list(&list, "path1");
+    add_string_list(&list, "path2");
+
+    ErrorCode result = path_manager_move_up(&list, 0);  /* 第一个元素无法上移 */
+
+    assert_int_equal(result, ERR_INVALID_INDEX);
+
+    clear_string_list(&list);
+}
+
+static void test_move_up_invalid_index(void **state)
+{
+    (void)state;
+    StringList list;
+    init_string_list(&list);
+    add_string_list(&list, "path1");
+    add_string_list(&list, "path2");
+
+    ErrorCode result = path_manager_move_up(&list, 5);  /* 越界 */
+
+    assert_int_not_equal(result, ERR_OK);
+
+    clear_string_list(&list);
+}
+
+static void test_move_up_single_element(void **state)
+{
+    (void)state;
+    StringList list;
+    init_string_list(&list);
+    add_string_list(&list, "path1");
+
+    ErrorCode result = path_manager_move_up(&list, 0);
+
+    assert_int_equal(result, ERR_INVALID_INDEX);
+    assert_string_equal(string_list_get(&list, 0), "path1");
+
+    clear_string_list(&list);
+}
+
+/* ==================== path_manager_move_down 测试 ==================== */
+
+static void test_move_down_normal(void **state)
+{
+    (void)state;
+    StringList list;
+    init_string_list(&list);
+    add_string_list(&list, "path1");
+    add_string_list(&list, "path2");
+    add_string_list(&list, "path3");
+
+    ErrorCode result = path_manager_move_down(&list, 1);
+
+    assert_int_equal(result, ERR_OK);
+    assert_string_equal(string_list_get(&list, 0), "path1");
+    assert_string_equal(string_list_get(&list, 1), "path3");
+    assert_string_equal(string_list_get(&list, 2), "path2");
+
+    clear_string_list(&list);
+}
+
+static void test_move_down_last_element(void **state)
+{
+    (void)state;
+    StringList list;
+    init_string_list(&list);
+    add_string_list(&list, "path1");
+    add_string_list(&list, "path2");
+
+    ErrorCode result = path_manager_move_down(&list, 1);  /* 最后一个元素无法下移 */
+
+    assert_int_equal(result, ERR_INVALID_INDEX);
+
+    clear_string_list(&list);
+}
+
+static void test_move_down_invalid_index(void **state)
+{
+    (void)state;
+    StringList list;
+    init_string_list(&list);
+    add_string_list(&list, "path1");
+    add_string_list(&list, "path2");
+
+    ErrorCode result = path_manager_move_down(&list, 5);  /* 越界 */
+
+    assert_int_not_equal(result, ERR_OK);
+
+    clear_string_list(&list);
+}
+
+static void test_move_down_single_element(void **state)
+{
+    (void)state;
+    StringList list;
+    init_string_list(&list);
+    add_string_list(&list, "path1");
+
+    ErrorCode result = path_manager_move_down(&list, 0);
+
+    assert_int_equal(result, ERR_INVALID_INDEX);
+    assert_string_equal(string_list_get(&list, 0), "path1");
+
+    clear_string_list(&list);
+}
+
+/* ==================== path_manager_clean 测试 ==================== */
+
+static void test_clean_no_invalid(void **state)
+{
+    (void)state;
+    is_path_valid_mock_enabled = 1;
+    is_path_valid_mock_return = 1;
+
+    StringList list;
+    init_string_list(&list);
+    add_string_list(&list, "C:\\Windows");
+    add_string_list(&list, "C:\\Program Files");
+
+    int before_count = list.count;
+    ErrorCode result = path_manager_clean(&list);
+
+    assert_int_equal(result, ERR_OK);
+    assert_int_equal(list.count, before_count);  /* 没有无效路径，不应删除 */
+
+    is_path_valid_mock_enabled = 0;
+    clear_string_list(&list);
+}
+
+static void test_clean_with_invalid(void **state)
+{
+    (void)state;
+    is_path_valid_mock_enabled = 1;
+    is_path_valid_mock_return = 0;  /* 所有路径都无效 */
+
+    StringList list;
+    init_string_list(&list);
+    add_string_list(&list, "C:\\Invalid1");
+    add_string_list(&list, "C:\\Invalid2");
+    add_string_list(&list, "C:\\Invalid3");
+
+    ErrorCode result = path_manager_clean(&list);
+
+    assert_int_equal(result, ERR_OK);
+    assert_int_equal(list.count, 0);  /* 所有路径都被删除 */
+
+    is_path_valid_mock_enabled = 0;
+    clear_string_list(&list);
+}
+
+static void test_clean_empty_list(void **state)
+{
+    (void)state;
+    StringList list;
+    init_string_list(&list);
+
+    ErrorCode result = path_manager_clean(&list);
+
+    assert_int_equal(result, ERR_OK);
+    assert_int_equal(list.count, 0);
+
+    clear_string_list(&list);
+}
+
+/* ==================== 主函数 ==================== */
+
+int main(void)
+{
+    const struct CMUnitTest tests[] = {
+        /* remove_at 测试 */
+        cmocka_unit_test(test_remove_at_normal),
+        cmocka_unit_test(test_remove_at_first),
+        cmocka_unit_test(test_remove_at_last),
+        cmocka_unit_test(test_remove_at_invalid_index),
+        cmocka_unit_test(test_remove_at_null),
+
+        /* move_up 测试 */
+        cmocka_unit_test(test_move_up_normal),
+        cmocka_unit_test(test_move_up_first_element),
+        cmocka_unit_test(test_move_up_invalid_index),
+        cmocka_unit_test(test_move_up_single_element),
+
+        /* move_down 测试 */
+        cmocka_unit_test(test_move_down_normal),
+        cmocka_unit_test(test_move_down_last_element),
+        cmocka_unit_test(test_move_down_invalid_index),
+        cmocka_unit_test(test_move_down_single_element),
+
+        /* clean 测试 */
+        cmocka_unit_test(test_clean_no_invalid),
+        cmocka_unit_test(test_clean_with_invalid),
+        cmocka_unit_test(test_clean_empty_list),
+    };
+
+    return cmocka_run_group_tests(tests, NULL, NULL);
+}
diff --git a/tests/unit/safe_string/CMakeLists.txt b/tests/unit/safe_string/CMakeLists.txt
new file mode 100644
index 0000000..2bb02e1
--- /dev/null
+++ b/tests/unit/safe_string/CMakeLists.txt
@@ -0,0 +1,16 @@
+# safe_string 单元测试
+add_executable(test_safe_string test_safe_string.c
+    ${CMAKE_SOURCE_DIR}/src/utils/safe_string.c
+)
+
+target_link_libraries(test_safe_string cmocka)
+
+target_include_directories(test_safe_string PRIVATE
+    ${CMAKE_SOURCE_DIR}/src/utils
+)
+
+# 定义 TESTING 宏以启用 mock
+target_compile_definitions(test_safe_string PRIVATE TESTING)
+
+# 添加测试
+add_test(NAME safe_string_test COMMAND test_safe_string)
diff --git a/tests/unit/safe_string/test_safe_string.c b/tests/unit/safe_string/test_safe_string.c
new file mode 100644
index 0000000..8a54199
--- /dev/null
+++ b/tests/unit/safe_string/test_safe_string.c
@@ -0,0 +1,209 @@
+/*
+ * safe_string.c 单元测试
+ * 测试安全字符串操作函数
+ */
+#include <stdarg.h>
+#include <stddef.h>
+#include <setjmp.h>
+#include <cmocka.h>
+#include <string.h>
+#include <stdlib.h>
+#include "utils/safe_string.h"
+
+/* ==================== safe_strcpy 测试 ==================== */
+
+static void test_safe_strcpy_normal(void **state)
+{
+    (void)state;
+    char dst[32];
+    const char *src = "Hello, World!";
+    char *result = safe_strcpy(dst, sizeof(dst), src);
+
+    assert_non_null(result);
+    assert_string_equal(dst, src);
+}
+
+static void test_safe_strcpy_truncation(void **state)
+{
+    (void)state;
+    char dst[8];
+    const char *src = "This is a long string";
+    char *result = safe_strcpy(dst, sizeof(dst), src);
+
+    assert_non_null(result);
+    assert_int_equal(strlen(dst), 7);  /* 截断到 7 字符 */
+    assert_memory_equal(dst, src, 7);  /* 前 7 字符相同 */
+    assert_int_equal(dst[7], '\0');
+}
+
+static void test_safe_strcpy_null_dst(void **state)
+{
+    (void)state;
+    const char *src = "test";
+    char *result = safe_strcpy(NULL, 10, src);
+    assert_null(result);
+}
+
+static void test_safe_strcpy_null_src(void **state)
+{
+    (void)state;
+    char dst[32];
+    char *result = safe_strcpy(dst, sizeof(dst), NULL);
+    assert_null(result);
+}
+
+static void test_safe_strcpy_zero_size(void **state)
+{
+    (void)state;
+    char dst[32];
+    char *result = safe_strcpy(dst, 0, "test");
+    assert_null(result);
+}
+
+static void test_safe_strcpy_exact_fit(void **state)
+{
+    (void)state;
+    char dst[6];
+    const char *src = "12345";  /* 5字符 + 1终止符 = 6 */
+    char *result = safe_strcpy(dst, sizeof(dst), src);
+
+    assert_non_null(result);
+    assert_string_equal(dst, "12345");
+}
+
+/* ==================== safe_strcat 测试 ==================== */
+
+static void test_safe_strcat_normal(void **state)
+{
+    (void)state;
+    char dst[32] = "Hello";
+    const char *src = ", World!";
+    char *result = safe_strcat(dst, sizeof(dst), src);
+
+    assert_non_null(result);
+    assert_string_equal(dst, "Hello, World!");
+}
+
+static void test_safe_strcat_truncation(void **state)
+{
+    (void)state;
+    char dst[12] = "Hello";
+    const char *src = ", World!";  /* 总长 12，但最后一个位置要放 \0 */
+    char *result = safe_strcat(dst, sizeof(dst), src);
+
+    assert_non_null(result);
+    /* dst 有 11 可用位置 (12-1)，"Hello" 占 5，还剩 6 */
+    /* ", World!" 有 9 字符，只能放 6 个字符 + \0 */
+    assert_true(strlen(dst) <= 11);
+}
+
+static void test_safe_strcat_null_dst(void **state)
+{
+    (void)state;
+    char dst[32] = "test";
+    char *result = safe_strcat(NULL, sizeof(dst), "src");
+    assert_null(result);
+}
+
+static void test_safe_strcat_null_src(void **state)
+{
+    (void)state;
+    char dst[32] = "test";
+    char *result = safe_strcat(dst, sizeof(dst), NULL);
+    /* src 为 NULL 时函数返回 NULL */
+    assert_null(result);
+}
+
+static void test_safe_strcat_empty_dst(void **state)
+{
+    (void)state;
+    char dst[32] = "";
+    const char *src = "Hello";
+    char *result = safe_strcat(dst, sizeof(dst), src);
+
+    assert_non_null(result);
+    assert_string_equal(dst, "Hello");
+}
+
+/* ==================== safe_strdup 测试 ==================== */
+
+static void test_safe_strdup_normal(void **state)
+{
+    (void)state;
+    const char *src = "Hello, World!";
+    char *result = safe_strdup(src);
+
+    assert_non_null(result);
+    assert_string_equal(result, src);
+    assert_ptr_not_equal(result, src);  /* 必须是新分配的内存 */
+
+    free(result);
+}
+
+static void test_safe_strdup_null(void **state)
+{
+    (void)state;
+    char *result = safe_strdup(NULL);
+    assert_null(result);
+}
+
+static void test_safe_strdup_empty_string(void **state)
+{
+    (void)state;
+    const char *src = "";
+    char *result = safe_strdup(src);
+
+    assert_non_null(result);
+    assert_string_equal(result, "");
+
+    free(result);
+}
+
+static void test_safe_strdup_long_string(void **state)
+{
+    (void)state;
+    /* 构造一个 510 字符的字符串 */
+    char src[511];
+    for (int i = 0; i < 510; i++) {
+        src[i] = 'A';
+    }
+    src[510] = '\0';
+
+    char *result = safe_strdup(src);
+
+    assert_non_null(result);
+    assert_int_equal(strlen(result), 510);
+    assert_memory_equal(result, src, 510);
+
+    free(result);
+}
+
+/* ==================== 主函数 ==================== */
+
+int main(void)
+{
+    const struct CMUnitTest tests[] = {
+        /* safe_strcpy 测试 */
+        cmocka_unit_test(test_safe_strcpy_normal),
+        cmocka_unit_test(test_safe_strcpy_truncation),
+        cmocka_unit_test(test_safe_strcpy_null_dst),
+        cmocka_unit_test(test_safe_strcpy_null_src),
+        cmocka_unit_test(test_safe_strcpy_zero_size),
+        cmocka_unit_test(test_safe_strcpy_exact_fit),
+
+        /* safe_strcat 测试 */
+        cmocka_unit_test(test_safe_strcat_normal),
+        cmocka_unit_test(test_safe_strcat_truncation),
+        cmocka_unit_test(test_safe_strcat_null_dst),
+        cmocka_unit_test(test_safe_strcat_null_src),
+        cmocka_unit_test(test_safe_strcat_empty_dst),
+
+        /* safe_strdup 测试 */
+        cmocka_unit_test(test_safe_strdup_normal),
+        cmocka_unit_test(test_safe_strdup_null),
+        cmocka_unit_test(test_safe_strdup_empty_string),
+        cmocka_unit_test(test_safe_strdup_long_string),
+    };
+
+    return cmocka_run_group_tests(tests, NULL, NULL);
+}
diff --git a/tests/unit/string_ext/CMakeLists.txt b/tests/unit/string_ext/CMakeLists.txt
new file mode 100644
index 0000000..27fb94a
--- /dev/null
+++ b/tests/unit/string_ext/CMakeLists.txt
@@ -0,0 +1,18 @@
+# string_ext 单元测试
+add_executable(test_string_ext test_string_ext.c
+    ${CMAKE_SOURCE_DIR}/src/utils/string_ext.c
+    ${CMAKE_SOURCE_DIR}/src/utils/safe_string.c
+)
+
+target_link_libraries(test_string_ext cmocka)
+
+target_include_directories(test_string_ext PRIVATE
+    ${CMAKE_SOURCE_DIR}/src/utils
+    ${CMAKE_SOURCE_DIR}/tests/mocks
+)
+
+# 定义 TESTING 宏和 REPLACE_WINDOWS_API 以启用 mock
+target_compile_definitions(test_string_ext PRIVATE TESTING REPLACE_WINDOWS_API)
+
+# 添加测试
+add_test(NAME string_ext_test COMMAND test_string_ext)
diff --git a/tests/unit/string_ext/test_string_ext.c b/tests/unit/string_ext/test_string_ext.c
new file mode 100644
index 0000000..1edb428
--- /dev/null
+++ b/tests/unit/string_ext/test_string_ext.c
@@ -0,0 +1,354 @@
+/*
+ * string_ext.c 单元测试
+ * 测试字符串扩展函数和 StringList 操作
+ */
+#include <stdarg.h>
+#include <stddef.h>
+#include <setjmp.h>
+#include <cmocka.h>
+#include <string.h>
+#include <stdlib.h>
+#include "utils/string_ext.h"
+#include "mock_windows.h"
+
+/* ==================== Mock 计数器 ==================== */
+int mock_MultiByteToWideChar_call_count = 0;
+int mock_WideCharToMultiByte_call_count = 0;
+static int mock_MB2WC_return = 0;
+static int mock_WC2MB_return = 0;
+
+void mock_set_MultiByteToWideChar_return(int ret) {
+    mock_MB2WC_return = ret;
+}
+
+void mock_set_WideCharToMultiByte_return(int ret) {
+    mock_WC2MB_return = ret;
+}
+
+/* ==================== Mock 实现 ==================== */
+
+int mock_MultiByteToWideChar(
+    UINT CodePage,
+    DWORD dwFlags,
+    LPCSTR lpMultiByteStr,
+    int cbMultiByte,
+    LPWSTR lpWideCharStr,
+    int cchWideChar)
+{
+    (void)CodePage;
+    (void)dwFlags;
+    mock_MultiByteToWideChar_call_count++;
+
+    if (!lpMultiByteStr || cbMultiByte == 0)
+        return 0;
+
+    int len = (cbMultiByte == -1) ? strlen(lpMultiByteStr) : cbMultiByte;
+
+    /* 简单 ASCII 转宽字符 */
+    if (lpWideCharStr && cchWideChar > 0) {
+        int copy_len = (cchWideChar < len + 1) ? cchWideChar - 1 : len;
+        for (int i = 0; i < copy_len; i++) {
+            lpWideCharStr[i] = (wchar_t)lpMultiByteStr[i];
+        }
+        lpWideCharStr[copy_len] = L'\0';
+    }
+
+    return mock_MB2WC_return > 0 ? mock_MB2WC_return : (len + 1);
+}
+
+int mock_WideCharToMultiByte(
+    UINT CodePage,
+    DWORD dwFlags,
+    LPCWSTR lpWideCharStr,
+    int cchWideChar,
+    LPSTR lpMultiByteStr,
+    int cbMultiByte,
+    LPCSTR lpDefaultChar,
+    LPBOOL lpUsedDefaultChar)
+{
+    (void)CodePage;
+    (void)dwFlags;
+    (void)lpDefaultChar;
+    (void)lpUsedDefaultChar;
+    mock_WideCharToMultiByte_call_count++;
+
+    if (!lpWideCharStr || cchWideChar == 0)
+        return 0;
+
+    int len = (cchWideChar == -1) ? wcslen(lpWideCharStr) : cchWideChar;
+
+    if (lpMultiByteStr && cbMultiByte > 0) {
+        int copy_len = (cbMultiByte < len + 1) ? cbMultiByte - 1 : len;
+        for (int i = 0; i < copy_len; i++) {
+            lpMultiByteStr[i] = (char)lpWideCharStr[i];
+        }
+        lpMultiByteStr[copy_len] = '\0';
+    }
+
+    return mock_WC2MB_return > 0 ? mock_WC2MB_return : (len + 1);
+}
+
+/* ==================== StringList 测试 ==================== */
+
+static void test_init_string_list(void **state)
+{
+    (void)state;
+    StringList list;
+    list.items = (void *)0x1234;  /* 初始化前设置垃圾值 */
+    list.count = 999;
+    list.capacity = 999;
+
+    init_string_list(&list);
+
+    /* init_string_list 将 items 设置为 NULL，count 和 capacity 设为 0 */
+    assert_null(list.items);
+    assert_int_equal(list.count, 0);
+    assert_int_equal(list.capacity, 0);
+
+    /* clear_string_list 对 NULL items 应该安全处理 */
+    clear_string_list(&list);
+}
+
+static void test_add_string_list_single(void **state)
+{
+    (void)state;
+    StringList list;
+    init_string_list(&list);
+
+    add_string_list(&list, "C:\\Windows");
+
+    assert_int_equal(list.count, 1);
+    assert_string_equal(string_list_get(&list, 0), "C:\\Windows");
+
+    clear_string_list(&list);
+}
+
+static void test_add_string_list_multiple(void **state)
+{
+    (void)state;
+    StringList list;
+    init_string_list(&list);
+
+    add_string_list(&list, "C:\\Windows");
+    add_string_list(&list, "C:\\Program Files");
+    add_string_list(&list, "D:\\Tools");
+
+    assert_int_equal(list.count, 3);
+    assert_string_equal(string_list_get(&list, 0), "C:\\Windows");
+    assert_string_equal(string_list_get(&list, 1), "C:\\Program Files");
+    assert_string_equal(string_list_get(&list, 2), "D:\\Tools");
+
+    clear_string_list(&list);
+}
+
+static void test_string_list_get_out_of_bounds(void **state)
+{
+    (void)state;
+    StringList list;
+    init_string_list(&list);
+
+    add_string_list(&list, "test");
+
+    assert_null(string_list_get(&list, -1));
+    assert_null(string_list_get(&list, 1));
+    assert_null(string_list_get(&list, 100));
+
+    clear_string_list(&list);
+}
+
+static void test_string_list_get_null_list(void **state)
+{
+    (void)state;
+    assert_null(string_list_get(NULL, 0));
+}
+
+static void test_string_list_set_normal(void **state)
+{
+    (void)state;
+    StringList list;
+    init_string_list(&list);
+
+    add_string_list(&list, "original");
+    int result = string_list_set(&list, 0, "modified");
+
+    assert_int_equal(result, 0);
+    assert_string_equal(string_list_get(&list, 0), "modified");
+
+    clear_string_list(&list);
+}
+
+static void test_string_list_set_out_of_bounds(void **state)
+{
+    (void)state;
+    StringList list;
+    init_string_list(&list);
+
+    add_string_list(&list, "test");
+    int result = string_list_set(&list, 5, "modified");
+
+    assert_int_equal(result, -1);
+
+    clear_string_list(&list);
+}
+
+static void test_string_list_set_null_list(void **state)
+{
+    (void)state;
+    int result = string_list_set(NULL, 0, "test");
+    assert_int_equal(result, -1);
+}
+
+static void test_clear_string_list(void **state)
+{
+    (void)state;
+    StringList list;
+    init_string_list(&list);
+
+    add_string_list(&list, "item1");
+    add_string_list(&list, "item2");
+    add_string_list(&list, "item3");
+
+    clear_string_list(&list);
+
+    assert_int_equal(list.count, 0);
+    assert_null(list.items);
+}
+
+/* ==================== 编码转换测试 ==================== */
+
+static void test_utf8_to_wide_normal(void **state)
+{
+    (void)state;
+    const char *utf8_str = "Hello";
+
+    wchar_t *result = utf8_to_wide(utf8_str);
+
+    if (result) {
+        assert_true(wcscmp(result, L"Hello") == 0);
+        free(result);
+    }
+}
+
+static void test_utf8_to_wide_null(void **state)
+{
+    (void)state;
+    wchar_t *result = utf8_to_wide(NULL);
+    assert_null(result);
+}
+
+static void test_wide_to_utf8_normal(void **state)
+{
+    (void)state;
+    const wchar_t *wide_str = L"World";
+
+    char *result = wide_to_utf8(wide_str);
+
+    if (result) {
+        assert_string_equal(result, "World");
+        free(result);
+    }
+}
+
+static void test_wide_to_utf8_null(void **state)
+{
+    (void)state;
+    char *result = wide_to_utf8(NULL);
+    assert_null(result);
+}
+
+/* ==================== stristr 测试 ==================== */
+
+static void test_stristr_found(void **state)
+{
+    (void)state;
+    const char *haystack = "The quick brown fox";
+    const char *needle = "quick";
+
+    char *result = stristr(haystack, needle);
+
+    assert_non_null(result);
+    assert_ptr_equal(result, haystack + 4);  /* "quick" 在 "The " 之后 */
+}
+
+static void test_stristr_not_found(void **state)
+{
+    (void)state;
+    const char *haystack = "The quick brown fox";
+    const char *needle = "jumps";
+
+    char *result = stristr(haystack, needle);
+
+    assert_null(result);
+}
+
+static void test_stristr_case_insensitive(void **state)
+{
+    (void)state;
+    const char *haystack = "The QUICK brown fox";
+    const char *needle = "quick";
+
+    char *result = stristr(haystack, needle);
+
+    assert_non_null(result);
+}
+
+static void test_stristr_null_haystack(void **state)
+{
+    (void)state;
+    char *result = stristr(NULL, "test");
+    assert_null(result);
+}
+
+static void test_stristr_null_needle(void **state)
+{
+    (void)state;
+    char *result = stristr("test", NULL);
+    assert_null(result);
+}
+
+static void test_stristr_empty_needle(void **state)
+{
+    (void)state;
+    const char *haystack = "The quick brown fox";
+    const char *needle = "";
+
+    char *result = stristr(haystack, needle);
+
+    /* 空字符串应该返回原字符串首地址 */
+    assert_non_null(result);
+    assert_ptr_equal(result, haystack);
+}
+
+/* ==================== 主函数 ==================== */
+
+int main(void)
+{
+    const struct CMUnitTest tests[] = {
+        /* StringList 测试 */
+        cmocka_unit_test(test_init_string_list),
+        cmocka_unit_test(test_add_string_list_single),
+        cmocka_unit_test(test_add_string_list_multiple),
+        cmocka_unit_test(test_string_list_get_out_of_bounds),
+        cmocka_unit_test(test_string_list_get_null_list),
+        cmocka_unit_test(test_string_list_set_normal),
+        cmocka_unit_test(test_string_list_set_out_of_bounds),
+        cmocka_unit_test(test_string_list_set_null_list),
+        cmocka_unit_test(test_clear_string_list),
+
+        /* 编码转换测试 */
+        cmocka_unit_test(test_utf8_to_wide_normal),
+        cmocka_unit_test(test_utf8_to_wide_null),
+        cmocka_unit_test(test_wide_to_utf8_normal),
+        cmocka_unit_test(test_wide_to_utf8_null),
+
+        /* stristr 测试 */
+        cmocka_unit_test(test_stristr_found),
+        cmocka_unit_test(test_stristr_not_found),
+        cmocka_unit_test(test_stristr_case_insensitive),
+        cmocka_unit_test(test_stristr_null_haystack),
+        cmocka_unit_test(test_stristr_null_needle),
+        cmocka_unit_test(test_stristr_empty_needle),
+    };
+
+    return cmocka_run_group_tests(tests, NULL, NULL);
+}