diff --git a/src/g2_2025_grade_calculator_pkg/CMakeLists.txt b/src/g2_2025_grade_calculator_pkg/CMakeLists.txt
index 796be24..bb0c855 100644
--- a/src/g2_2025_grade_calculator_pkg/CMakeLists.txt
+++ b/src/g2_2025_grade_calculator_pkg/CMakeLists.txt
@@ -8,13 +8,13 @@ endif()
 # external packages
 include(FetchContent)
 
-FetchContent_Declare(
+fetchcontent_declare(
     tomlplusplus
     GIT_REPOSITORY https://github.com/marzer/tomlplusplus.git
     GIT_TAG v3.4.0
 )
 
-FetchContent_MakeAvailable(tomlplusplus)
+fetchcontent_makeavailable(tomlplusplus)
 
 # find dependencies
 find_package(ament_cmake REQUIRED)
@@ -64,7 +64,7 @@ add_executable(retake_scheduler
 )
 ament_target_dependencies(retake_scheduler rclcpp g2_2025_interfaces)
 
-install (
+install(
     TARGETS
         exam_result_generator
         final_grade_determinator
@@ -75,15 +75,39 @@ install (
 )
 
 if(BUILD_TESTING)
-  find_package(ament_lint_auto REQUIRED)
-  # the following line skips the linter which checks for copyrights
-  # comment the line when a copyright and license is added to all source files
-  set(ament_cmake_copyright_FOUND TRUE)
-  # the following line skips cpplint (only works in a git repo)
-  # comment the line when this package is in a git repo and when
-  # a copyright and license is added to all source files
-  set(ament_cmake_cpplint_FOUND TRUE)
-  ament_lint_auto_find_test_dependencies()
+  find_package(ament_cmake_gtest REQUIRED)
+
+  # Add gtest for ConfigManager
+  ament_add_gtest(${PROJECT_NAME}_test_config_manager
+    test/ConfigManager.test.cpp
+    src/config/ConfigManager.cpp
+  )
+  target_include_directories(${PROJECT_NAME}_test_config_manager PRIVATE
+    ${CMAKE_CURRENT_SOURCE_DIR}/src
+  )
+  ament_target_dependencies(${PROJECT_NAME}_test_config_manager
+    rclcpp
+  )
+  target_link_libraries(${PROJECT_NAME}_test_config_manager
+    tomlplusplus::tomlplusplus
+  )
+
+  # Add gtest for DatabaseManager
+  ament_add_gtest(${PROJECT_NAME}_test_database_manager
+    test/DatabaseManager.test.cpp
+    src/database/DatabaseManager.cpp
+    src/config/ConfigManager.cpp
+  )
+  target_include_directories(${PROJECT_NAME}_test_database_manager PRIVATE
+    ${CMAKE_CURRENT_SOURCE_DIR}/src
+  )
+  ament_target_dependencies(${PROJECT_NAME}_test_database_manager
+    rclcpp
+    g2_2025_interfaces
+  )
+  target_link_libraries(${PROJECT_NAME}_test_database_manager
+    pqxx pq tomlplusplus::tomlplusplus
+  )
 endif()
 
 ament_package()
diff --git a/src/g2_2025_grade_calculator_pkg/package.xml b/src/g2_2025_grade_calculator_pkg/package.xml
index 31cb72c..fb3cd5e 100644
--- a/src/g2_2025_grade_calculator_pkg/package.xml
+++ b/src/g2_2025_grade_calculator_pkg/package.xml
@@ -12,9 +12,6 @@
   <depend>rclcpp</depend>
   <depend>g2_2025_interfaces</depend>
 
-  <test_depend>ament_lint_auto</test_depend>
-  <test_depend>ament_lint_common</test_depend>
-
   <export>
     <build_type>ament_cmake</build_type>
   </export>
diff --git a/src/g2_2025_grade_calculator_pkg/test/ConfigManager.test.cpp b/src/g2_2025_grade_calculator_pkg/test/ConfigManager.test.cpp
new file mode 100644
index 0000000..69b0068
--- /dev/null
+++ b/src/g2_2025_grade_calculator_pkg/test/ConfigManager.test.cpp
@@ -0,0 +1,135 @@
+#include <filesystem>
+#include <fstream>
+#include <gtest/gtest.h>
+#include <rclcpp/rclcpp.hpp>
+
+#include "config/ConfigManager.hpp"
+
+using namespace assignments::one;
+
+static const std::string TEST_CONFIG_CONTENT = R"(
+[database]
+host = "test_host"
+port = 1234
+dbname = "test_db"
+user = "test_user"
+password = "test_password"
+timeout = 60
+ssl = true
+
+[database.pool]
+min_connections = 2
+max_connections = 20
+)";
+
+static const std::string TEST_CONFIG_NO_POOL_CONTENT = R"(
+[database]
+host = "localhost"
+port = 5432
+dbname = "grades"
+user = "postgres"
+password = "postgres"
+)";
+
+
+class ConfigManagerTest : public ::testing::Test {
+protected:
+    void SetUp() override {
+        rclcpp::init(0, nullptr);
+        node_ = std::make_shared<rclcpp::Node>("test_config_node");
+    }
+
+    void TearDown() override {
+        // Clean up temporary files
+        if (std::filesystem::exists(temp_config_file_)) {
+            std::filesystem::remove(temp_config_file_);
+        }
+
+        node_.reset();
+        rclcpp::shutdown();
+    }
+
+    void create_temp_config_file() {
+        temp_config_file_ = "test_config.toml";
+        std::ofstream file(temp_config_file_);
+        file << TEST_CONFIG_CONTENT;
+        file.close();
+    }
+
+    std::shared_ptr<rclcpp::Node> node_;
+    std::string temp_config_file_;
+};
+
+TEST_F(ConfigManagerTest, ConstructorTest) {
+    // Test ConfigManager can be constructed with logger
+    ConfigManager config_manager(node_->get_logger());
+    // Constructor should not crash
+    SUCCEED();
+}
+
+TEST_F(ConfigManagerTest, LoadValidConfigTest) {
+    create_temp_config_file();
+
+    ConfigManager config_manager(node_->get_logger());
+    bool result = config_manager.load_config(temp_config_file_);
+
+    EXPECT_TRUE(result);
+    EXPECT_TRUE(config_manager.is_loaded());
+}
+
+TEST_F(ConfigManagerTest, LoadInvalidFileTest) {
+    ConfigManager config_manager(node_->get_logger());
+    bool result = config_manager.load_config("non_existent_file.toml");
+
+    EXPECT_FALSE(result);
+    EXPECT_FALSE(config_manager.is_loaded());
+}
+
+TEST_F(ConfigManagerTest, DatabaseConfigParsingTest) {
+    create_temp_config_file();
+
+    ConfigManager config_manager(node_->get_logger());
+    config_manager.load_config(temp_config_file_);
+
+    auto db_config = config_manager.get_database_config();
+
+    ASSERT_TRUE(db_config.has_value());
+    EXPECT_EQ(db_config->host, "test_host");
+    EXPECT_EQ(db_config->port, 1234);
+    EXPECT_EQ(db_config->dbname, "test_db");
+    EXPECT_EQ(db_config->user, "test_user");
+    EXPECT_EQ(db_config->password, "test_password");
+    EXPECT_EQ(db_config->timeout, 60);
+    EXPECT_TRUE(db_config->ssl);
+    EXPECT_EQ(db_config->min_connections, 2);
+    EXPECT_EQ(db_config->max_connections, 20);
+}
+
+TEST_F(ConfigManagerTest, DatabaseConfigWithoutPoolTest) {
+    // Create config without pool section
+    std::ofstream file("test_config_no_pool.toml");
+    file << TEST_CONFIG_NO_POOL_CONTENT;
+    file.close();
+
+    ConfigManager config_manager(node_->get_logger());
+    config_manager.load_config("test_config_no_pool.toml");
+
+    auto db_config = config_manager.get_database_config();
+
+    ASSERT_TRUE(db_config.has_value());
+    EXPECT_EQ(db_config->host, "localhost");
+    EXPECT_EQ(db_config->port, 5432);
+    EXPECT_EQ(db_config->min_connections, 1);  // default
+    EXPECT_EQ(db_config->max_connections, 10); // default
+
+    std::filesystem::remove("test_config_no_pool.toml");
+}
+
+TEST_F(ConfigManagerTest, GetConfigWithoutLoadingTest) {
+    ConfigManager config_manager(node_->get_logger());
+
+    auto db_config = config_manager.get_database_config();
+
+    EXPECT_FALSE(db_config.has_value());
+    EXPECT_FALSE(config_manager.is_loaded());
+}
diff --git a/src/g2_2025_grade_calculator_pkg/test/DatabaseManager.test.cpp b/src/g2_2025_grade_calculator_pkg/test/DatabaseManager.test.cpp
new file mode 100644
index 0000000..417dd8e
--- /dev/null
+++ b/src/g2_2025_grade_calculator_pkg/test/DatabaseManager.test.cpp
@@ -0,0 +1,79 @@
+#include <gtest/gtest.h>
+#include <rclcpp/rclcpp.hpp>
+
+#include "database/DatabaseManager.hpp"
+#include "database/StudentCourse.hpp"
+
+using namespace assignments::one;
+
+class DatabaseManagerTest : public ::testing::Test {
+protected:
+    void SetUp() override {
+        rclcpp::init(0, nullptr);
+
+        node_ = std::make_shared<rclcpp::Node>("test_db_node");
+        db_manager_ = std::make_unique<DatabaseManager>(node_->get_logger());
+    }
+
+    void TearDown() override {
+        db_manager_.reset();
+        node_.reset();
+        rclcpp::shutdown();
+    }
+
+    std::shared_ptr<rclcpp::Node> node_;
+    std::unique_ptr<DatabaseManager> db_manager_;
+};
+
+TEST_F(DatabaseManagerTest, ConstructorTest) {
+    // Test DatabaseManager can be constructed
+    ASSERT_NE(db_manager_, nullptr);
+}
+
+TEST_F(DatabaseManagerTest, ConnectionStatusTest) {
+    bool status = db_manager_->is_connected();
+
+    EXPECT_TRUE(status == true || status == false);
+}
+
+TEST_F(DatabaseManagerTest, QueuePendingCombinationsTest) {
+    auto combinations = db_manager_->queue_pending_combinations();
+
+    EXPECT_GE(combinations.size(), 0);
+}
+
+TEST_F(DatabaseManagerTest, StoreExamResultTest) {
+    bool result = db_manager_->store_exam_result("TestStudent", "TestCourse", 85);
+
+    EXPECT_TRUE(result == true || result == false);
+}
+
+TEST_F(DatabaseManagerTest, EnrollStudentTest) {
+    StudentCourse sc;
+    sc.student_name = "TestStudent";
+    sc.course_name = "TestCourse";
+
+    bool result = db_manager_->enroll_student_into_course(sc);
+
+    EXPECT_TRUE(result == true || result == false);
+}
+
+TEST_F(DatabaseManagerTest, GetFinalGradeTest) {
+    StudentCourse sc;
+    sc.student_name = "NonExistentStudent";
+    sc.course_name = "NonExistentCourse";
+
+    int grade = db_manager_->get_final_course_grade(sc);
+
+    EXPECT_EQ(grade, -1);
+}
+
+TEST_F(DatabaseManagerTest, StoreFinalResultTest) {
+    StudentCourse sc;
+    sc.student_name = "TestStudent";
+    sc.course_name = "TestCourse";
+
+    bool result = db_manager_->store_final_course_result(sc, 3, 75);
+
+    EXPECT_TRUE(result == true || result == false);
+}