diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index b6da90d..dcabc5f 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -3,7 +3,7 @@ set(BACKEND_EXETUABLE_NAME "zts-core")
 if(OJ_TEST_BACKEND)
   set(BACKEND_EXETUABLE_NAME "code")
 endif()
-add_executable(${BACKEND_EXETUABLE_NAME} main.cpp engine.cpp utils.cpp data.cpp)
+add_executable(${BACKEND_EXETUABLE_NAME} main.cpp engine.cpp utils.cpp data.cpp user_system.cpp train_system.cpp transaction_system.cpp)
 target_link_libraries(${BACKEND_EXETUABLE_NAME} argparse)
 target_link_libraries(${BACKEND_EXETUABLE_NAME} spdlog::spdlog)
 target_link_libraries(${BACKEND_EXETUABLE_NAME} sockpp)
diff --git a/src/engine.cpp b/src/engine.cpp
index b697120..9b74c7c 100644
--- a/src/engine.cpp
+++ b/src/engine.cpp
@@ -97,317 +97,6 @@ std::string TicketSystemEngine::Execute(const std::string &command) {
   throw std::invalid_argument("Invalid command.");
 }
 
-std::string TicketSystemEngine::AddUser(const std::string &command) {
-  command_id_t command_id;
-  sscanf(command.c_str(), "[%llu]", &command_id);
-  LOG->debug("command id: {}", command_id);
-  LOG->debug("command: {}", command);
-  std::stringstream command_stream(command), response_stream;
-  std::string token, cur_username, username, password, name, mailAddr;
-  uint8_t privilege;
-  command_stream >> token >> token;
-  while (command_stream >> token) {
-    switch (token[1]) {
-      case 'c': {
-        command_stream >> cur_username;
-        break;
-      }
-      case 'u': {
-        command_stream >> username;
-        break;
-      }
-      case 'p': {
-        command_stream >> password;
-        break;
-      }
-      case 'n': {
-        command_stream >> name;
-        break;
-      }
-      case 'm': {
-        command_stream >> mailAddr;
-        break;
-      }
-      case 'g': {
-        int tmp;
-        command_stream >> tmp;
-        privilege = tmp;
-        break;
-      }
-      default:
-        throw std::invalid_argument("arg parse fatal error in add_user");
-    }
-  }
-  if (user_data.size() == 0) {
-    // special case, no need to check current user's privilege
-    FullUserData dat;
-    dat.privilege = 10;
-    strcpy(dat.username, username.c_str());
-    dat.password_hash = SplitMix64Hash(password);
-    strcpy(dat.name, name.c_str());
-    strcpy(dat.mailAddr, mailAddr.c_str());
-    user_data.Put(SplitMix64Hash(username), dat);
-    LOG->debug("stored user_name hash: {}", SplitMix64Hash(username));
-    LOG->debug("stored user_name: {}", dat.username);
-    LOG->debug("stored password hash: {}", dat.password_hash);
-    LOG->debug("stored name: {}", dat.name);
-    LOG->debug("stored mailAddr: {}", dat.mailAddr);
-    LOG->debug("stored privilege: {}", dat.privilege);
-    response_stream << '[' << command_id << "] 0";
-    return response_stream.str();
-  }
-  hash_t current_user_username_hash = SplitMix64Hash(cur_username);
-  if (online_users.find(current_user_username_hash) == online_users.end()) {
-    response_stream << '[' << command_id << "] -1";
-    return response_stream.str();
-  }
-  if (privilege >= online_users[current_user_username_hash]) {
-    response_stream << '[' << command_id << "] -1";
-    return response_stream.str();
-  }
-  hash_t new_user_username_hash = SplitMix64Hash(username);
-  if (user_data.HasKey(new_user_username_hash)) {
-    response_stream << '[' << command_id << "] -1";
-    return response_stream.str();
-  }
-  FullUserData dat;
-  dat.privilege = privilege;
-  strcpy(dat.username, username.c_str());
-  dat.password_hash = SplitMix64Hash(password);
-  strcpy(dat.name, name.c_str());
-  strcpy(dat.mailAddr, mailAddr.c_str());
-  user_data.Put(new_user_username_hash, dat);
-  LOG->debug("stored user_name hash: {}", new_user_username_hash);
-  LOG->debug("stored user_name: {}", dat.username);
-  LOG->debug("stored password hash: {}", dat.password_hash);
-  LOG->debug("stored name: {}", dat.name);
-  LOG->debug("stored mailAddr: {}", dat.mailAddr);
-  LOG->debug("stored privilege: {}", dat.privilege);
-  response_stream << '[' << command_id << "] 0";
-  return response_stream.str();
-}
-
-std::string TicketSystemEngine::LoginUser(const std::string &command) {
-  command_id_t command_id;
-  sscanf(command.c_str(), "[%llu]", &command_id);
-  LOG->debug("command id: {}", command_id);
-  std::stringstream command_stream(command), response_stream;
-  std::string token, user_name, password;
-  command_stream >> token >> token;
-  while (command_stream >> token) {
-    switch (token[1]) {
-      case 'u': {
-        command_stream >> user_name;
-        break;
-      }
-      case 'p': {
-        command_stream >> password;
-        break;
-      }
-      default:
-        throw std::invalid_argument("arg parse fatal error in login");
-    }
-  }
-  hash_t user_name_hash = SplitMix64Hash(user_name);
-  hash_t password_hash = SplitMix64Hash(password);
-  if (online_users.find(user_name_hash) != online_users.end()) {
-    response_stream << '[' << command_id << "] -1";
-    return response_stream.str();
-  }
-  FullUserData dat;
-  try {
-    user_data.Get(user_name_hash, dat);
-    if (dat.password_hash != password_hash) {
-      response_stream << '[' << command_id << "] -1";
-      return response_stream.str();
-    }
-  } catch (std::runtime_error &e) {
-    response_stream << '[' << command_id << "] -1";
-    return response_stream.str();
-  }
-  online_users[user_name_hash] = dat.privilege;
-  response_stream << '[' << command_id << "] 0";
-  return response_stream.str();
-}
-
-std::string TicketSystemEngine::LogoutUser(const std::string &command) {
-  command_id_t command_id;
-  sscanf(command.c_str(), "[%llu]", &command_id);
-  LOG->debug("command id: {}", command_id);
-  std::stringstream command_stream(command), response_stream;
-  std::string token, user_name;
-  command_stream >> token >> token;
-  while (command_stream >> token) {
-    switch (token[1]) {
-      case 'u': {
-        command_stream >> user_name;
-        break;
-      }
-      default:
-        throw std::invalid_argument("arg parse fatal error in logout");
-    }
-  }
-  hash_t user_name_hash = SplitMix64Hash(user_name);
-  if (online_users.find(user_name_hash) == online_users.end()) {
-    response_stream << '[' << command_id << "] -1";
-    return response_stream.str();
-  }
-  online_users.erase(user_name_hash);
-  response_stream << '[' << command_id << "] 0";
-  return response_stream.str();
-}
-
-std::string TicketSystemEngine::QueryProfile(const std::string &command) {
-  command_id_t command_id;
-  sscanf(command.c_str(), "[%llu]", &command_id);
-  LOG->debug("command id: {}", command_id);
-  std::stringstream command_stream(command), response_stream;
-  std::string token, current_user_name, user_name;
-  command_stream >> token >> token;
-  while (command_stream >> token) {
-    switch (token[1]) {
-      case 'c': {
-        command_stream >> current_user_name;
-        break;
-      }
-      case 'u': {
-        command_stream >> user_name;
-        break;
-      }
-      default:
-        throw std::invalid_argument("arg parse fatal error in query_profile");
-    }
-  }
-  hash_t current_user_name_hash = SplitMix64Hash(current_user_name);
-  hash_t user_name_hash = SplitMix64Hash(user_name);
-  if (online_users.find(current_user_name_hash) == online_users.end()) {
-    response_stream << '[' << command_id << "] -1";
-    return response_stream.str();
-  }
-  FullUserData dat;
-  LOG->debug("user_name_hash: {}", user_name_hash);
-  LOG->debug("mailAddr: {}", dat.mailAddr);
-  if (current_user_name_hash != user_name_hash) {
-    try {
-      user_data.Get(user_name_hash, dat);
-      if (online_users[current_user_name_hash] <= dat.privilege) {
-        response_stream << '[' << command_id << "] -1";
-        return response_stream.str();
-      }
-    } catch (std::runtime_error &e) {
-      response_stream << '[' << command_id << "] -1";
-      return response_stream.str();
-    }
-  } else {
-    user_data.Get(user_name_hash, dat);
-  }
-  LOG->debug("mailAddr: {}", dat.mailAddr);
-  response_stream << '[' << command_id << "] " << dat.username << ' ' << dat.name << ' ' << dat.mailAddr << ' '
-                  << static_cast<int>(dat.privilege);
-  return response_stream.str();
-}
-
-std::string TicketSystemEngine::ModifyProfile(const std::string &command) {
-  command_id_t command_id;
-  sscanf(command.c_str(), "[%llu]", &command_id);
-  LOG->debug("command id: {}", command_id);
-  std::stringstream command_stream(command), response_stream;
-  std::string token, current_user_name, user_name, password, name, mailAddr;
-  uint8_t privilege = 11;
-  command_stream >> token >> token;
-  while (command_stream >> token) {
-    switch (token[1]) {
-      case 'c': {
-        command_stream >> current_user_name;
-        break;
-      }
-      case 'u': {
-        command_stream >> user_name;
-        break;
-      }
-      case 'p': {
-        command_stream >> password;
-        break;
-      }
-      case 'n': {
-        command_stream >> name;
-        break;
-      }
-      case 'm': {
-        command_stream >> mailAddr;
-        break;
-      }
-      case 'g': {
-        int tmp;
-        command_stream >> tmp;
-        privilege = tmp;
-        break;
-      }
-      default:
-        throw std::invalid_argument("arg parse fatal error in add_user");
-    }
-  }
-  hash_t current_user_name_hash = SplitMix64Hash(current_user_name);
-  hash_t user_name_hash = SplitMix64Hash(user_name);
-  if (online_users.find(current_user_name_hash) == online_users.end()) {
-    response_stream << '[' << command_id << "] -1";
-    return response_stream.str();
-  }
-  FullUserData dat;
-  if (current_user_name_hash != user_name_hash) {
-    try {
-      user_data.Get(user_name_hash, dat);
-      if (online_users[current_user_name_hash] <= dat.privilege) {
-        response_stream << '[' << command_id << "] -1";
-        return response_stream.str();
-      }
-    } catch (std::runtime_error &e) {
-      response_stream << '[' << command_id << "] -1";
-      return response_stream.str();
-    }
-  } else {
-    user_data.Get(user_name_hash, dat);
-  }
-  if (privilege != 11 && privilege >= online_users[current_user_name_hash]) {
-    response_stream << '[' << command_id << "] -1";
-    return response_stream.str();
-  }
-  if (privilege != 11) {
-    dat.privilege = privilege;
-  }
-  if (password != "") {
-    dat.password_hash = SplitMix64Hash(password);
-  }
-  if (name != "") {
-    strcpy(dat.name, name.c_str());
-  }
-  if (mailAddr != "") {
-    strcpy(dat.mailAddr, mailAddr.c_str());
-  }
-  user_data.Put(user_name_hash, dat);
-  response_stream << '[' << command_id << "] " << dat.username << ' ' << dat.name << ' ' << dat.mailAddr << ' '
-                  << static_cast<int>(dat.privilege);
-  return response_stream.str();
-}
-
-std::string TicketSystemEngine::AddTrain(const std::string &command) { return "AddTrain"; }
-
-std::string TicketSystemEngine::DeleteTrain(const std::string &command) { return "DeleteTrain"; }
-
-std::string TicketSystemEngine::ReleaseTrain(const std::string &command) { return "ReleaseTrain"; }
-
-std::string TicketSystemEngine::QueryTrain(const std::string &command) { return "QueryTrain"; }
-
-std::string TicketSystemEngine::BuyTicket(const std::string &command) { return "BuyTicket"; }
-
-std::string TicketSystemEngine::QueryOrder(const std::string &command) { return "QueryOrder"; }
-
-std::string TicketSystemEngine::RefundTicket(const std::string &command) { return "RefundTicket"; }
-
-std::string TicketSystemEngine::QueryTransfer(const std::string &command) { return "QueryTransfer"; }
-
-std::string TicketSystemEngine::QueryTicket(const std::string &command) { return "QueryTicket"; }
-
 std::string TicketSystemEngine::Clean() { return "Clean"; }
 
 std::string TicketSystemEngine::Exit(const std::string &command) {
diff --git a/src/train_system.cpp b/src/train_system.cpp
new file mode 100644
index 0000000..6ee1089
--- /dev/null
+++ b/src/train_system.cpp
@@ -0,0 +1,17 @@
+#include <cstring>
+#include <sstream>
+#include <stdexcept>
+#include <string>
+#include <utility>
+#include "basic_defs.h"
+#include "data.h"
+#include "engine.h"
+#include "utils.h"
+
+std::string TicketSystemEngine::AddTrain(const std::string &command) { return "AddTrain"; }
+
+std::string TicketSystemEngine::DeleteTrain(const std::string &command) { return "DeleteTrain"; }
+
+std::string TicketSystemEngine::ReleaseTrain(const std::string &command) { return "ReleaseTrain"; }
+
+std::string TicketSystemEngine::QueryTrain(const std::string &command) { return "QueryTrain"; }
\ No newline at end of file
diff --git a/src/transaction_system.cpp b/src/transaction_system.cpp
new file mode 100644
index 0000000..26d7755
--- /dev/null
+++ b/src/transaction_system.cpp
@@ -0,0 +1,19 @@
+#include <cstring>
+#include <sstream>
+#include <stdexcept>
+#include <string>
+#include <utility>
+#include "basic_defs.h"
+#include "data.h"
+#include "engine.h"
+#include "utils.h"
+
+std::string TicketSystemEngine::BuyTicket(const std::string &command) { return "BuyTicket"; }
+
+std::string TicketSystemEngine::QueryOrder(const std::string &command) { return "QueryOrder"; }
+
+std::string TicketSystemEngine::RefundTicket(const std::string &command) { return "RefundTicket"; }
+
+std::string TicketSystemEngine::QueryTransfer(const std::string &command) { return "QueryTransfer"; }
+
+std::string TicketSystemEngine::QueryTicket(const std::string &command) { return "QueryTicket"; }
\ No newline at end of file
diff --git a/src/user_system.cpp b/src/user_system.cpp
new file mode 100644
index 0000000..be327f3
--- /dev/null
+++ b/src/user_system.cpp
@@ -0,0 +1,302 @@
+#include <cstring>
+#include <sstream>
+#include <stdexcept>
+#include <string>
+#include <utility>
+#include "basic_defs.h"
+#include "data.h"
+#include "engine.h"
+#include "utils.h"
+
+std::string TicketSystemEngine::AddUser(const std::string &command) {
+  command_id_t command_id;
+  sscanf(command.c_str(), "[%llu]", &command_id);
+  LOG->debug("command id: {}", command_id);
+  LOG->debug("command: {}", command);
+  std::stringstream command_stream(command), response_stream;
+  std::string token, cur_username, username, password, name, mailAddr;
+  uint8_t privilege;
+  command_stream >> token >> token;
+  while (command_stream >> token) {
+    switch (token[1]) {
+      case 'c': {
+        command_stream >> cur_username;
+        break;
+      }
+      case 'u': {
+        command_stream >> username;
+        break;
+      }
+      case 'p': {
+        command_stream >> password;
+        break;
+      }
+      case 'n': {
+        command_stream >> name;
+        break;
+      }
+      case 'm': {
+        command_stream >> mailAddr;
+        break;
+      }
+      case 'g': {
+        int tmp;
+        command_stream >> tmp;
+        privilege = tmp;
+        break;
+      }
+      default:
+        throw std::invalid_argument("arg parse fatal error in add_user");
+    }
+  }
+  if (user_data.size() == 0) {
+    // special case, no need to check current user's privilege
+    FullUserData dat;
+    dat.privilege = 10;
+    strcpy(dat.username, username.c_str());
+    dat.password_hash = SplitMix64Hash(password);
+    strcpy(dat.name, name.c_str());
+    strcpy(dat.mailAddr, mailAddr.c_str());
+    user_data.Put(SplitMix64Hash(username), dat);
+    LOG->debug("stored user_name hash: {}", SplitMix64Hash(username));
+    LOG->debug("stored user_name: {}", dat.username);
+    LOG->debug("stored password hash: {}", dat.password_hash);
+    LOG->debug("stored name: {}", dat.name);
+    LOG->debug("stored mailAddr: {}", dat.mailAddr);
+    LOG->debug("stored privilege: {}", dat.privilege);
+    response_stream << '[' << command_id << "] 0";
+    return response_stream.str();
+  }
+  hash_t current_user_username_hash = SplitMix64Hash(cur_username);
+  if (online_users.find(current_user_username_hash) == online_users.end()) {
+    response_stream << '[' << command_id << "] -1";
+    return response_stream.str();
+  }
+  if (privilege >= online_users[current_user_username_hash]) {
+    response_stream << '[' << command_id << "] -1";
+    return response_stream.str();
+  }
+  hash_t new_user_username_hash = SplitMix64Hash(username);
+  if (user_data.HasKey(new_user_username_hash)) {
+    response_stream << '[' << command_id << "] -1";
+    return response_stream.str();
+  }
+  FullUserData dat;
+  dat.privilege = privilege;
+  strcpy(dat.username, username.c_str());
+  dat.password_hash = SplitMix64Hash(password);
+  strcpy(dat.name, name.c_str());
+  strcpy(dat.mailAddr, mailAddr.c_str());
+  user_data.Put(new_user_username_hash, dat);
+  LOG->debug("stored user_name hash: {}", new_user_username_hash);
+  LOG->debug("stored user_name: {}", dat.username);
+  LOG->debug("stored password hash: {}", dat.password_hash);
+  LOG->debug("stored name: {}", dat.name);
+  LOG->debug("stored mailAddr: {}", dat.mailAddr);
+  LOG->debug("stored privilege: {}", dat.privilege);
+  response_stream << '[' << command_id << "] 0";
+  return response_stream.str();
+}
+
+std::string TicketSystemEngine::LoginUser(const std::string &command) {
+  command_id_t command_id;
+  sscanf(command.c_str(), "[%llu]", &command_id);
+  LOG->debug("command id: {}", command_id);
+  std::stringstream command_stream(command), response_stream;
+  std::string token, user_name, password;
+  command_stream >> token >> token;
+  while (command_stream >> token) {
+    switch (token[1]) {
+      case 'u': {
+        command_stream >> user_name;
+        break;
+      }
+      case 'p': {
+        command_stream >> password;
+        break;
+      }
+      default:
+        throw std::invalid_argument("arg parse fatal error in login");
+    }
+  }
+  hash_t user_name_hash = SplitMix64Hash(user_name);
+  hash_t password_hash = SplitMix64Hash(password);
+  if (online_users.find(user_name_hash) != online_users.end()) {
+    response_stream << '[' << command_id << "] -1";
+    return response_stream.str();
+  }
+  FullUserData dat;
+  try {
+    user_data.Get(user_name_hash, dat);
+    if (dat.password_hash != password_hash) {
+      response_stream << '[' << command_id << "] -1";
+      return response_stream.str();
+    }
+  } catch (std::runtime_error &e) {
+    response_stream << '[' << command_id << "] -1";
+    return response_stream.str();
+  }
+  online_users[user_name_hash] = dat.privilege;
+  response_stream << '[' << command_id << "] 0";
+  return response_stream.str();
+}
+
+std::string TicketSystemEngine::LogoutUser(const std::string &command) {
+  command_id_t command_id;
+  sscanf(command.c_str(), "[%llu]", &command_id);
+  LOG->debug("command id: {}", command_id);
+  std::stringstream command_stream(command), response_stream;
+  std::string token, user_name;
+  command_stream >> token >> token;
+  while (command_stream >> token) {
+    switch (token[1]) {
+      case 'u': {
+        command_stream >> user_name;
+        break;
+      }
+      default:
+        throw std::invalid_argument("arg parse fatal error in logout");
+    }
+  }
+  hash_t user_name_hash = SplitMix64Hash(user_name);
+  if (online_users.find(user_name_hash) == online_users.end()) {
+    response_stream << '[' << command_id << "] -1";
+    return response_stream.str();
+  }
+  online_users.erase(user_name_hash);
+  response_stream << '[' << command_id << "] 0";
+  return response_stream.str();
+}
+
+std::string TicketSystemEngine::QueryProfile(const std::string &command) {
+  command_id_t command_id;
+  sscanf(command.c_str(), "[%llu]", &command_id);
+  LOG->debug("command id: {}", command_id);
+  std::stringstream command_stream(command), response_stream;
+  std::string token, current_user_name, user_name;
+  command_stream >> token >> token;
+  while (command_stream >> token) {
+    switch (token[1]) {
+      case 'c': {
+        command_stream >> current_user_name;
+        break;
+      }
+      case 'u': {
+        command_stream >> user_name;
+        break;
+      }
+      default:
+        throw std::invalid_argument("arg parse fatal error in query_profile");
+    }
+  }
+  hash_t current_user_name_hash = SplitMix64Hash(current_user_name);
+  hash_t user_name_hash = SplitMix64Hash(user_name);
+  if (online_users.find(current_user_name_hash) == online_users.end()) {
+    response_stream << '[' << command_id << "] -1";
+    return response_stream.str();
+  }
+  FullUserData dat;
+  LOG->debug("user_name_hash: {}", user_name_hash);
+  LOG->debug("mailAddr: {}", dat.mailAddr);
+  if (current_user_name_hash != user_name_hash) {
+    try {
+      user_data.Get(user_name_hash, dat);
+      if (online_users[current_user_name_hash] <= dat.privilege) {
+        response_stream << '[' << command_id << "] -1";
+        return response_stream.str();
+      }
+    } catch (std::runtime_error &e) {
+      response_stream << '[' << command_id << "] -1";
+      return response_stream.str();
+    }
+  } else {
+    user_data.Get(user_name_hash, dat);
+  }
+  LOG->debug("mailAddr: {}", dat.mailAddr);
+  response_stream << '[' << command_id << "] " << dat.username << ' ' << dat.name << ' ' << dat.mailAddr << ' '
+                  << static_cast<int>(dat.privilege);
+  return response_stream.str();
+}
+
+std::string TicketSystemEngine::ModifyProfile(const std::string &command) {
+  command_id_t command_id;
+  sscanf(command.c_str(), "[%llu]", &command_id);
+  LOG->debug("command id: {}", command_id);
+  std::stringstream command_stream(command), response_stream;
+  std::string token, current_user_name, user_name, password, name, mailAddr;
+  uint8_t privilege = 11;
+  command_stream >> token >> token;
+  while (command_stream >> token) {
+    switch (token[1]) {
+      case 'c': {
+        command_stream >> current_user_name;
+        break;
+      }
+      case 'u': {
+        command_stream >> user_name;
+        break;
+      }
+      case 'p': {
+        command_stream >> password;
+        break;
+      }
+      case 'n': {
+        command_stream >> name;
+        break;
+      }
+      case 'm': {
+        command_stream >> mailAddr;
+        break;
+      }
+      case 'g': {
+        int tmp;
+        command_stream >> tmp;
+        privilege = tmp;
+        break;
+      }
+      default:
+        throw std::invalid_argument("arg parse fatal error in add_user");
+    }
+  }
+  hash_t current_user_name_hash = SplitMix64Hash(current_user_name);
+  hash_t user_name_hash = SplitMix64Hash(user_name);
+  if (online_users.find(current_user_name_hash) == online_users.end()) {
+    response_stream << '[' << command_id << "] -1";
+    return response_stream.str();
+  }
+  FullUserData dat;
+  if (current_user_name_hash != user_name_hash) {
+    try {
+      user_data.Get(user_name_hash, dat);
+      if (online_users[current_user_name_hash] <= dat.privilege) {
+        response_stream << '[' << command_id << "] -1";
+        return response_stream.str();
+      }
+    } catch (std::runtime_error &e) {
+      response_stream << '[' << command_id << "] -1";
+      return response_stream.str();
+    }
+  } else {
+    user_data.Get(user_name_hash, dat);
+  }
+  if (privilege != 11 && privilege >= online_users[current_user_name_hash]) {
+    response_stream << '[' << command_id << "] -1";
+    return response_stream.str();
+  }
+  if (privilege != 11) {
+    dat.privilege = privilege;
+  }
+  if (password != "") {
+    dat.password_hash = SplitMix64Hash(password);
+  }
+  if (name != "") {
+    strcpy(dat.name, name.c_str());
+  }
+  if (mailAddr != "") {
+    strcpy(dat.mailAddr, mailAddr.c_str());
+  }
+  user_data.Put(user_name_hash, dat);
+  response_stream << '[' << command_id << "] " << dat.username << ' ' << dat.name << ' ' << dat.mailAddr << ' '
+                  << static_cast<int>(dat.privilege);
+  return response_stream.str();
+}
\ No newline at end of file
diff --git a/test/ojtest.py b/test/ojtest.py
index 4cf2efa..f6bcc60 100755
--- a/test/ojtest.py
+++ b/test/ojtest.py
@@ -92,6 +92,7 @@ def RunTestGroup(name):
       has_unpassed_test=True
       continue
     if disk_limit<0:
+      print("removing disk files")
       disk_limit = -disk_limit
       # remove directory /tmp/$name
       shutil.rmtree(playground_dir, ignore_errors=True)